This is beyond inappropriate and is not at all comparable to screaming in public.

Both of them are inappropriate. The point is that if a mentally ill person squeezes someone's butt, the potential damage is that person feeling uncomfortable. If someone randomly starts screaming, people might be confused, they might think that the person is injured or hurt, it could even potentially cause people people to act chaotically and try to flee the area if they don't know what's going on. Neither of them are particularly dangerous compared to, say, a mentally ill person who randomly attacks people, but the screaming clearly has more of a potential to cause damage in the moment.

Sexual assualt is physically and mentally damaging and is never ever acceptable.

I mean touching someone's butt isn't physically damaging. Some forms of sexual assault certainly are, but not this one. And of course it isn't acceptable, mentally ill people act unacceptably all the time. I'm not saying it's ok, I'm just saying that it's not always something that actually put's people in danger to the extent that keeping them out of public becomes a priority before helping them get above their problems.

If you cannot be in public without sexually assaulting people, you cannot be in public.

Yeah, but if you can get treatment, but their a slight risk that you might still randomly grab someone's butt now and then in the process of getting better, it's not really putting anyone in danger to be in public.

Stop being so dismissive of sexual asault.

I'm not. Sexual assault can be horrible. But if I had to choose between more mentally ill people getting treatment and being allowed to live more normal lives, with the occasional risk of a butt grab, and locking up even more mentally ill people in prison to rot away, I would choose the first. I'd happily have my butt grabbed every day without my consent if it meant one more mentally ill who is a step closer to living a life like the one I am lucky enough to be able to live. I've worked with mentally ill people before, and I've worked with sexual assault victims before, and I have a lot of sympathy for both.