Religions change slowly, someone once commented that if you read the old testament and concider that it was written by a nation that lived in a very hostile area all of the rules make sense. It is a desert survival guide:
Don't eat pork because it spoils easily and you might kill yourself (and maybe it spreads and endangers everyone else as well) by eating it
Cutting off your foreskin makes cleaning yourself easier and reduces chances of getting something nasty. (Which might kill you and everyone else.)
If you take a crap in the desert don't do it in your camp, go somewhere else and crap in a hole which you then cover. (If the crusaders had read the bible and followed rules like this they might have actually kept the middle east.)
Having sex with many different people increases the chances of an STD spreading and killing everyone.
The punishments that the old testament orders are sever, often lethal, because if one moron does something stupid it might kill the whole tribe. So killing off a moron who risks everyones lives is a smart choice.
These days most christians aren't living in a desert so many of those codes have became outdated though.