I'm running a small (< 20) group of people. We organize day-long events every weekend, where new members are also welcome. Anyone can join our Facebook group where we advertise our events.
At our latest event, a person showed up who seemed to be cool in the beginning, but ended up making the rest of the day miserable to some (most) of the regulars.
Without going into too much detail, this was due to one of his personality traits which I'm pretty sure he won't be able to change any time soon. I'd like to point out that the person is friendly and 'cool', but pretty much unbearable after an hour or two. He didn't do anything outrageous or inappropriate, but he was extremely annoying after a while.
After the event, I sent him an email, politely suggesting that he might not fit in well with us because of this particular behavior. Unfortunately, the message wasn't clear enough. His response was something along the lines of "Haha, yeah I can [be like that] sometimes. Anyways, I enjoyed the [event], I'll be happy to join you next time!".
How do I tell this person that I would like him to leave our group, without embarrassing him? (Or at least minimizing the embarrassment.)