This has never happened before and he sees nothing wrong with this behaviour. He would tell everyone if I let him. I have no idea if this is normal for a man with dementia. Truthfully I find it disgusting. He thinks he did it all his life..
It's known as Inappropriate Sexual Behavior *ISB* and it does happen to some people who suffer with dementia/Alz. He may start wanting sex from you all the time, too, regardless of whether he's capable of actually having sex..........the urges may convince him he IS. Call his doctor and let him know, and hopefully, the doctor is aware of this symptom and can prescribe a medication to calm him down. If the doctor is unaware of this symptom, it's time to find a new doctor or neurologist who's better versed in dementia/Alz.
I’ve never been in this situation but I would likely do two things. First, inquire with his doctor about meds to reduce this behavior. And secondly, block his ability to access. Just like you can use parental controls to block channels on a tv, there has to be a way to block this. Sorry for what you’re dealing with
Good luck!