Bible laws that go against current laws.
Exodus21:15 And he that smiteth his father, or his mother, shall be surely put to death.
21:17 And he that curseth his father, or his mother, shall surely be put to death.
Last time I checked, we had capital punishment enforcement for first-degree murder, as the smiting in this verse implies.
Cursing, in this instance, is WAAAAAAAAAY more than saying a few naughty four-letter words. It involved conduct and behavior that brought shame, misfortune, and dishonor on a family.
Bible comands you to kill Rebelous children,Kill people who cheat on their wives,Kill homosexuals.
Such things are illegal to do by mans law but are a sin NOT to do by gods law.
Until recently, we had laws on the books that made homosexuality and adultery illegal and punishable under the law. Granted, such were not capital offenses. But, they were consider illegal (and still considered immoral behavior). Furthermore, as it is in our society, such were to be tried and convicted in a court of law (i.e. the judges, mentioned in Exodus 21, where you got those verses), before sentencing of any kind was carried out.
As for the killing rebellious children bit, particularly in Deut. 21, the verse says nothing of the sort. Like many other readers, you have assumed that the offender (the rebellious son) is a child, largely because we live in a society where people believe that they are only subject to their parents' authority as kids.
Read again the rest of verse 20,
This our son is stubborn and rebellious, he will not obey our voice; he is a glutton, and a drunkard. That sounds more like an adult than a kid to me. In other words, this passage is not suggesting that the judges of Israel heave rocks at little Ezekiel, for his not eating his manna or picking up his G.I. Jehosephat action figures off the floor.
Men, even as adults, stayed with their parents and were under their authority, until they got married, espeically considering that the parents arranged the marriages in the first place.
Furthermore, where does it state that is a sin, for the judges not to inflict the maximum sentence for violators of such laws?