Here's an anecdote I remembered in the wake of the story about Steve Bannon being invited to, then uninvited from, The New Yorker's conference.
I was in a student group in college, and we'd post to the school's mailing list when we had our meetings. One time, a kid none of us knew replied to say he'd join us when we met at a local pizzeria. Cool—the more the merrier.
However, it turned out he was a fervent proselytizer, and he was on a mission to convert people to Calvinism…
…He would turn every conversation into it. He brought a Bible and quoted from it. He had this medieval-style conviction that he had to save souls from damnation—it wasn't an option for him NOT to do this. I’m talking about a person who walked around carrying a Bible under his arm, like he was in some Southern Gothic movie.
After that meeting, he kept posting to our mailing list, and asked when we'd meet again…
…Our faculty guide asked him to un-join the group because he was being an unproductive distraction. The kid went straight to the Dean and filed a religious discrimination complaint, saying he had as much right to be in this group as anyone else.
Now, it turned out he had also done this before, and was known around the campus for trying to infiltrate various groups. The office kind of rolled their eyes, went through the due process, and told him they found no wrongdoing…
…This gave us something to collectively "wtf" and rant about for a while, but it ultimately sapped our energy. The mailing list dried up because we didn't want to bait him into it anymore.
I have no clue what became of him. One thing I know is that engaging him further wouldn't have helped. He wanted us to convert; nothing else would do. Even when he was gone, he ended up dominating our group because we talked about nothing BUT him when we talked.
The end.