That’s because there is an objective morality and we know the differences between right and wrong naturally. But society can twist them, and it is now and has done many times before.

But let’s also not pretend that God’s rules are all great, either. If the guy who enacted a worldwide genocide and commands fathers to kill their sons is your moral compass

You are seriously taking these concepts out of context to the point of dishonesty. For the “commands fathers to kill their sons” I assume you mean the narrative about Abraham and Isaac. The whole point of that is in a world where people were being sacrificed to a god, the true God didn’t require human sacrifices from men. In fact, the whole story in of itself is a prophecy

Genesis 22:8, 11-14

Abraham said, “God will provide for himself the lamb for a burnt offering, my son.” So they went both of them together.

But the angel of the Lord called to him from heaven and said, “Abraham, Abraham!” And he said, “Here I am.” He said, “Do not lay your hand on the boy or do anything to him, for now I know that you fear God, seeing you have not withheld your son, your only son, from me.” And Abraham lifted up his eyes and looked, and behold, behind him was a ram, caught in a thicket by his horns. And Abraham went and took the ram and offered it up as a burnt offering instead of his son.

Interesting that it was said that God will provide a lamb, but instead there was provided a ram?

So Abraham called the name of that place, “The Lord will provide” as it is said to this day, “On the mount of the Lord it shall be provided.”

It shall be provided.

John 1:28-29

These things took place in Bethany across the Jordan, where John was baptizing. The next day he saw Jesus coming toward him, and said, “Behold, the Lamb of God, who takes away the sin of the world!

As for the flood- That is just God purging evil from the world. He is well within His rights to do that.