An interesting thought I read a long time ago - but it is not clear if it is an argument pro or con:
People use VR to train how to perform various tasks; and I believe the military and law enforcement might use (or already use) VR to simulate violent encounters. That indicates that it actually makes you better at that task - which involves killing people; and assumedly murderers could do the same.
However, that also means that people should be allowed to use them for self defense, and for training to become police officers/soldiers (especially in the US; where people may claim it is part of their militia training).