Again, there's forgeted up stuff in every religions holy book. I could say Christians who aren't doing the crazy stuff their book says to do aren't proper Christians. But that doesn't get anyone anywhere, so stop singling out one religion as being okay to do it to
It's a little different for Christians. Often we don't follow all the old testament rules because the old testament laws were set up under the original covenant God had with Abraham and his descendants.
This law was sort of overriden by in the new testament when Jesus died for everyone's sins and were accounted for. Now the laws are more of a loose guideline moreso than something that needs to be followed to a T.
As an example, many animals in the old testament were considered unclean, such as pigs, lizards, various bugs, etc. People speculate that this is partly because those foods listed were likely to get people sick in the ancient days before anyone knew anything about cleaning stuff, but I digress.
In Acts 10, Peter gets a vision from the Lord saying, essentially, that all food is now clean, and that it's fine to eat these foods. This partly shows how the Law is mostly void now, due to the new covenant. There are other examples that I can't think of right now.
Essentially, Christians should live by the 2 core principles Jesus set forth: Love God, and love others as you love yourself. (see Matthew 23:37)
That's the true spirit and point of the law. Not all of us do, obviously, but that's basically it. That's why we don't stone kids for disrespecting their parents.
If I've lost any of you due to Christianese or what have you, then please, do not hesitate to ask me to elaborate.
EDIT: Man I'm so bad a posting long posts without numerous grammatical errors...