I've namechanged for this.
Yesterday I started a new activity for the first time. One of the men in the group showed me in, but as he was doing so, I suddenly felt his hand on my bum. It wasn't just momentary - it was almost as if he was guiding me in by putting his hand on my bum. At the time I was taken by surprise and didn't say anything - I was just shocked, and didn't want to make a fuss within 2 minutes of arriving.
During the activity I found out that the man is one of the organisers of the group and that his wife also attends the group.
I didn't like what he did and don't think it's acceptable, but am wondering if I'm over-reacting? Also, I don't think there's anything I can do about it. As he's a regular and I'm new, I think if I mentioned it I'd just come across as a trouble-maker (I'm assuming no one's complained before or he wouldn't have been given the task of showing new people in).
I wouldn't have to be alone with this man and don't feel in any danger or anything, but also don't feel it's acceptable that I'll be on edge and watching where his hands are if he's close to me.
So I think my AIBU is am I over-reacting and also what, if anything, would you do? Thanks.