Every time I have ever exposed myself to mafia as witch they just murder me the next night, it is much better to find their killer and use him to kill off the other players so you are in control of who they kill, maybe even their own (you have no way to tell who their own are), instead of being random targeted or murdered by them after exposing yourself to them.
I think there needs to be the option of there being some kind of consequence to discourage murdering your own side, mafia has no reason to ever let the witch live.
As it is now if you want to have a chance of winning you need to find their killer and control them (which will likely annoy them) to protect yourself. Unless they get a majority and lynch you... which is a reason to keep their numbers low too.