Islam critiqued denounces injustice; Khidr controversy?

In answer to the video "The Quran's "Replacement Theology"

Pure monotheism necessitates that nothing may escape God's power, and this includes man's freewill. It is entirely encompassed by Allah. In His Quran, Allah gives examples of persons and informs us of His foreknowledge concerning them. He then shows how their freewill can either be allowed to continue or is taken away: 

-a young boy was prevented from using his freewill and become a source of suffering for the pious parents. He was slain by one of Allah's envoys whom the commentaries have named "Khidr", under Allah's command.

-Abu Lahab or the people of Nuh were left to use their freewill and continue in their evil ways until death

As to the first example, Khidr demonstrates that appearance and reality are intrinsically different, so different that only mystic insight, an insight sometimes even beyond the grasp of the greatests of prophets, can reveal to us what is apparent and what is real. Even a great prophet's intellect cannot always comprehend the Divine will, wisdom and justice. Nothing is ethically absolute from the limited viewpoint of humans, even prophets. Sometimes things may even seem unethical when looking at the narrow picture but become perfectly ethical in the bigger picture. This is according to one humbling Quranic principle that

12:76"above every possessor of knowledge is (one) (more) knowing"

with God being the ultimate possessor of all knowledge, hidden and apparent, allowing what He wills to be temporarily shared with His creation 2:255. This concept transpires throughout the Quran in many different ways, in order to put man's propensity for arrogance and self-sufficiency in check. For example right after sura fatiha, the plea in which man is spiritually humbled and taught to seek guidance from a superior entity, in the next sura man's intellect is immediately humbled, right from the start through the huruf muqattaat/disjointed letters. These seemingly simple alphabetical letters are found in every Arabic text, available for all, but out of which Allah created a book the equivalent of which no intellect can produce. That intellectual, creative superiority can be observed virtually anywhere in the system of the universe; just as man makes bricks and ceramics out of soil, Allah creates thousands of flowers and plants, fruits and animals as well as man, out of the same materials.

As a testimony of one's understanding of that principle, one should therefore ask the All-Knowing to be increased in knowledge 20:114, just like the prophet David teaches in his Psalms119:27-34 to ask God to open one's intellect to grasping the Torah, increase one's knowledge and understanding of His precepts. The Quran primarily teaches humanity how to think before imparting knowledge.

The story of Moses and the servant of God reminds that there is a supremely wise Sovereign behind the system of the universe and the everyday events one encounters. Whatever Allah does, or allows to occur, is done according to His wisdom and justice that takes into account a global perspective whose intricacies none can truly fathom but Him. 
Nothing passes out of His control, not even man's freewill. Man is judged according to his level of freewill, the extent he is able to exercise it, given his own circumstances. That is why Allah is the True and Final Judge. He is Ahkam al-hakimin/the best of all the judges 11:45,95:8.

So God could and does sometimes "save" someone by taking away his freewill and preventing him from doing evil, or He could and does sometimes leave him to use his freewill and bare full responsibility for his actions.

Both scenarios are allowed according to Allah's wisdom and justice and a believer, just like a prophet of God, knows the limits of his understanding when it comes to the will of the Creator in certain situations.

For those who, like Abu Lahab, are left to commit so many sins until they die, the Quran says that hell does not necessarly have to be an eternal abode for them. Those who did nothing in this life to deserve God's mercy and forgiveness in the hereafter, will then have to wait for God's justice.

A person dies when his time, appointed by God for reasons known only to Him, has come. We will never know the higher reasons behind what often seems to us a premature death, we will never know what the person's life would've been like had it contined, and the repercusions it would've had on its environement. Life itself is a Divine blessing; no one has an entitlement to it. From this perspective the issue of demanding a continuation of life doesn’t arise, let alone for one to ask for a reason for its non-continuation.

The boy killed by Khidr had reached his appointed time of death and was slain, under God's command just like a person would die by God's will from an accident, illness, or at the hands of another person etc. The death of the boy was entirely dependent on Allah's command; Khidr, a servant of God who was given divine mercy and some knowledge of the unseen, was merely executing God's will just like a devastating earthquake only happens by Allah's will. This is somewhat comparable to the scheme which God explicitly states was revealed to Yusuf, an elaborate plan that may at first seem like an unfair situation but which ultimately had a higher good for all those involved 12:76. An innocent person, like this boy who still had not comitted any crime, cannot be taken unjustly by another human as per God's law, otherwise it would be murder. Khidr did not act on his own but by divine inspiration and knowledge of the unseen "and I did not do it of my own accord". Khidr was one among those whom God selects to execute His will in this world 18:65. He was made to see certain things which one could only be acquainted with through revelation, among them foresight into this particular child's future "and we feared lest he should make disobedience and ingratitude to come upon them". Khidr, and the other knowledgeable entities like him were not certain of what would have eventually occurred down the line but had strong basis for fearing that harm might befall his righteous parents, and thus desired that Allah might change the course of things so as to safeguard them. Ultimately it is Allah who decided for the appropriate course of action, and caused the child's death, through His servant.

Ibn Abbas reflected this notion when he answered an inquirer, telling him the prophet would not kill children so that person should not do it, unless that person had knowledge of the unseen, like Khidr, and acted upon a divine command

"unless you could know what Khadir had known about the child he killed".

This is a way of saying that no regular person would ever receive such authority. Similarily to Khidr, Angels are tasked with terminating human life, whomever the person might be, under God's command 4:97,32:11,6:61,16:28,47:27. It is therefore safe to assume that this unnamed servant of God was an angel in human form, as angels always appear in this world whenever they interract with human beings, several examples of these encounters are recorded in the Quran. A similar case of killing children occurs in the HB, although not originally decreed by God as is the case with Khidr, rather resulted from a prophet's invocations. Elisha invoked God's curse upon some taunting and impolite youngsters, and consequently 42 of them were slaugtered by bears 2Kings2:23-24. Jewish Oral tradition explains that

"neither in them nor in their descendants would there be any ‘sap’ of good deeds".

As God was promising to inflict massacre upon the Israelites for their transgressions, He explicitly stated that the newborns themselves will be targeted for slaying

Hos9:16"even when they give birth, I will slay the precious ones of their womb".

This is because should they multiply, more corruption would ensue

Hos14:1"they shall fall by the sword, their infants shall be dashed, and their pregnant women shall be ripped up".

Elsewhere, in the same spirit, the HB, instead of premature death, condones child disciplining through battery

Prov23:13-14"Do not withhold discipline from a child; when you strike him with a rod, he will not die. You shall strike him with a rod, and you will save his soul from the grave".

When Moses protested and asked Khidr the reason for slaying the boy, Khidr explained that according to the special knowledge granted to him by God, the boy was starting to become an evil and sinful person who would, through his own choices and actions, ultimately lead his believing parents astray. KHAWF means fear of credible danger, as is consistent with all its occurrences in the Quran. So, it is not fear as in suspicion/Dhann. Dhann is to hold an opinion upon uncertain evidence. Here is an instance where God unveils his reasons and plans behind one of his decrees. Allah had willed for that boy's life to end in order to allow a greater good: avoid him a sinful life and prevent the parents from going astray. God replaced him with one whose future choices would have good repercusions on himself and his environement, a future source of mercy for the parents.

The incident of the young boy is no different than the death of any person (whom Allah knows his future choices) except that in this case, we are given a glimpse of the Unseen: the future choices of the boy had he lived are explained, just as in Abu Lahab's case or the rejecters in the nation of Nuh 11:36-37 where we are informed that they will die as disbelievers. There is an interesting verse which encapsulates that idea

13:39"Allah erases what He pleases and establishes (likewise), and with Him is the basis of the Book".

God posesses the knowledge of all creation, allowing some of their deeds to materialize while erasing others, as in the kid slain by Khidr. His deeds are in God's knowledge had he continued living but their materialization was prevented, through his death.