I believe that even by first century standards thess laws were immoral.
I am no liberal, but I believe that Jesus did indeed repudiate the Mosiac Law.
Matthew 5:17-18 Think not that I am come to destroy the law, or the prophets: I am not come to destroy, but to fulfil. For verily I say unto you, Till heaven and earth pass, one jot or one tittle shall in no wise pass from the law, till all be fulfilled.
The problem is that makes the God of the OT different from the God of the NT. There have been a number of heresies from way back that took a line of thought similar to yours and followed it to its conclusion.
Remember this about the Canaanites. When the Romans (hardly the standard of virtue) fought the remnant of the Canaanites (the Carthaginians), they were horrified at the child sacrifice and other things that they did. Scipio razed Carthage both in retaliation for Hannibal, and to put an end to their horrible ways. These were not nice people whom God just decided to pick on.