Four questions for Christians

[Consilius]

Nowhere in the OT did God justify making slaves of neutral peoples, especially ones that had come across their borders seeking refuge.

If slavery is okay for certain people and not others, it is inconsistent.

Also note that the crime Egypt was punished for in the Tenth Plague was the killing of the Israelite babies. The executors of this offense were punished for allowing Israelite children to be killed by having their very own children killed. Therefore, they were punished exactly as they had been offended.

Killing babies is not a crime in God's eyes; he orders his soldiers to execute infant Amalekites. More inconsistency.

Your suggestion is arbitrary judgement. God cannot say that he will use his own justice system, because that would be unfair to the people being judged. These people would ask why the judge is being unfair, and the judge would say that the justice system he implements is infinitely more fair than anything you could imagine. The only reason that you don't think so is because of your imperfect human minds, also you were born in the wrong country at the wrong time period.

What, then, is the point of God having his own laws if he is going to judge others according to their own? And, where is the evidence for your assertion that he acts according to local laws? This is the first I've heard of this concept. Reeks of moral relativism, in fact.

Imagine God spoke to us today and told us that he will judge child-killing by killing children in the exact same way that the dead child was killed, and then insist that he is being just because the ancients had it right and we have deviated from 'the true path of righteousness'. That is your proposition.

Would you like to live in a society where every first born child in your nation was killed because some soldiers of your country committed this atrocity?

If capital punishment is OK for some people and not for others, then it is inconsistent.
Slaves in Israelite society were made of hostile peoples after war. People also sold themselves into slavery to pay off their debts.
Killing infants was, again, done to hostile peoples who had tried to kill Israelite infants. The Egyptians did it to the peaceful people they had enslaved.
Evidence of God treating OT people differently comes from Jesus' teaching on divorce: "Moses permitted you to divorce your wives because your hearts were hard. But it was not this way from the beginning."
This law code was not local. It was in practice in places all over the world. It was the norm for humanity. God used the general law code of whoever he punished so that the peoples he judged would only receive what they expected to receive. People who think what they are doing is good differ from people who perform the same act that know what they are doing is bad and know the penalty they are risking. Jesus preaches about ignorance of the truth in Luke 12:47:
"And that servant, which knew his lord's will, and prepared not himself, neither did according to his will, shall be beaten with many stripes. But he that knew not, and did commit things worthy of stripes, shall be beaten with few stripes. For to whomsoever much is given, of him shall be much required: and to whom men have committed much, of him they will ask the more."
God's law of "an eye for an eye, a tooth for a tooth" does not come out of nowhere. It comes from the laws and the general sense of justice that the world had figured out on its own (I do not assert that, it's an interesting argument). This imperfect law had come from Adam's sin. God still operated under the laws of these people because absolute retribution was what these people understood and it was what they operated on. When the time was right, Jesus completed the law by instituting God's law of mercy and forgiveness in perfection by making himself the ultimate example. However, God is still described as merciful in the OT (Exodus 33:19, Psalms 28:6).
The killing of the Hebrew babies, as well as the institution and the maintenance of their bondage in Egypt, was a national decision. There was no opposition to Pharaoh's ruling as recorded in the Bible, so there is no base to an argument saying so. Rather, the Egyptians are described in Exodus 10:1, 14:17, and 1 Samuel 6:6 as having the same attitude as their Pharaoh, the stubborness that caused the Plagues in the first place. Based on this, this would not only mean that I, as an individual, would have had decided that my country's soldiers were justified in killing children, but would have supported the idea itself when it was proposed.