This reminds me of something I read a lot about back in the 20th century, about the criminal justice system in general. (Not hate crimes. Just white-on-white murder and things like that.) They did a lot of research about the effects of different kind of sentencing, and it turned out making prison sentences longer didn't make them more effective at deterring crime. People don't stop and think "I want to kill my neighbor, and it's worth going to prison for 10 years to have him dead, but it wouldn't be worth 20 years." They think "I want to kill him and I won't get caught." Or they just don't think. There was a pilot program to reduce all sentences by 30%, across the board, keeping them all proportional to each other. (Might have been 50%.) They were still just as effective at deterring crime, and it saved lots of money. It didn't go anywhere, probably because the prison industrial complex is such a powerful lobbying group. I don't even remember what state tried it.

So I think we need to consider what it means for a law to be "effective." We have laws against rape, and those laws have value despite the ongoing prevalence of rape. Taking rape laws off the books would be a statement of what we consider important and worth protecting, and what we don't.