In 2016 I went to a comic con with a group of online friends, of which a couple of streamers with a decent sized community. F is in this community but nobody really speaks to him outside from what he says in stream chats and from what I know, nobody is really friends with him. He seems like a lonely individual but has very little friends as he often says weird things in chat.
The community was invited to meet up at the comic con and so was he. Me and the group met him there and he was awkward, to say the least. He has a habit of getting someones attention by grabbing someone by the upper arm (so firmly it hurts) and then talking very close to your face. He seems to do so more with girls, but maybe the guys were just quicker to push him off. He makes weird, sometimes racist comments. He commented on girl's boobs and how they were 'too fat' etc. He seems to have little to no understanding of how to behave in a social situation or what (not) to say. One of the girls wasn't feeling well due to low blood sugar and asked me to take her to the bathroom. F joined even though we said he shouldn't and made his way into the womens bathroom and it took us and 2 other ladies yelling at him before he would leave.
Fast forward to now, he somehow got my number from someone (we haven't talked anywhere outside the stream chat for 2 years) and invited me to join him and (so he said) S and M to a con at the end of the year. I barely speak S and M but we get along very well when we do. I asked S if she heard about it and she had only casually answered during a public stream that 'she'd think about it'.
He tried to get me to create a group chat in whatsapp, I think because he doesn't have phone numbers of S and M.
S, M and I agreed that it would be cool to go to the con and catch up, but we really have no interest in going with F. We're scared that if we go, he'll find out and meet up with us anyway.
How do we tell him we'd rather go alone, considering he has a difficult character? Or would, in dealing with someone who seems to have trouble accepting no, ignoring completely be the best solution?