Four questions for Christians

[Consilius]

You can't defend the Egyptians by saying that their only offense was thoughtrime because they had, in a very real and material sense, kept the Israelites from crossing Egypt's borders. During those ten plagues, the Israelites were still forced to bake bricks from mud under their Egyptian slavers.

Blame the individuals responsible for this.

Also, slavery wasn't a crime in the eyes of God (who not only told Moses he was allowed slaves but also gave him pointers on acquiring them). If God is punishing Egypt for the crime of slavery, then it is inconsistent and unjust when he does not prevent his own people from practicing the same institution.

And yes, an Egyptian judge in 2000 B.C. would kill my kid if I killed someone else's. This would be the punishment I would expect, and I would have absolutely no reason to even think that it was arbitrary in any way. Why should God use laws that just so happen to come from 21st century Europe? It would seem great to you, but terribly unjust to the Egyptian people.

God should be using laws infinitely more fair and just than anything we can come up with in the 21st century. If it took us only a few thousand years to do better than God...

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

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.
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.