I mentioned Lev 19:28 because you asked Finris why it was against his Jewish religion. Jews typically follow "the Law", as it is written in the Pentateuch (first 5 books of the Bible). I apologize if you know all this already - since you asked Finris, I'm going to proceed like you didn't.
As someone that has put his faith in Jesus Christ - realizing my salvation is completely by His grace and not by anything I have done or can do - I believe that I'm free from Old Testament Law because of the New Covenant. No one other than Jesus himself was ever able to perfectly follow OT Law. Those laws were given to Israel to show how futile it was to try to be holy. No one could ever follow them all. The New Covenant through Jesus freed us from the Law. But that doesn't mean that a believing Christian has license to continue willful sinning.
All that was probably more than asked for. But I do believe what I said above is Biblically accurate.