Could people who have the compulsion to be serial killers prevent themselves from murdering real people by doing it to holographic people?
In Voyager we saw Tuvok doing this to surpress a violent urge but I don't think it worked out too well, he still lost control.
Honestly though with all the incidents of holodeck characters becoming self aware, or becoming more human (the doctor on Voyager), I don't think people would use them for violence like they do on the show. I don't think people would play Call of Duty or GTA if sometimes the NPCs became full fledged people, I certainly wouldn't.
I think the truth is you could do an entire TV series just based on the holodeck and no space exploration at all. In fact I think that might be a pretty cool Star Trek show. Then if they really wanted to do a space based episode it can be a program on the holodeck.