I know it's hard, but people need to be able to just be like 'that is not okay' about these things, immediately.
When I was a drunken coke fiend (I mean I still kinda am just less often) I would pull this shit all the time and no one ever stopped me, but the second someone actually did take issue with it, it was like being punched in the chest. You suddenly realise holy shit, this is basically a sexual assault. I literally didn't even consider that in the moments it was happening, I was just a handsy drunk, but the second I got confronted about it - well, I've not done it since, except to people who are open to it in the first place.