That group sounds like a place where I wouldn't feel safe, or particularly welcomed.
The "homeless" analogy fails, because the Meetup isn't a city; it's an optional event run by volunteers. They don't owe a particular asshole membership, and they harmed the very group by allowing him to stay.
If we do want to try to stretch the analogy, with the meetup-as-a-social-gathering being our city, then the asshole was breaking one of the city's ordinances - a social rule of not being an asshole who harasses others. Homeless and homeful alike would be arrested and fined, or put in jail, if they flung bricks through the windows; someone who's breaking social norms and making others feel unsafe ought to be expelled from the group.
The "homeless" analogy fails, because the Meetup isn't a city; it's an optional event run by volunteers. They don't owe a particular asshole membership, and they harmed the very group by allowing him to stay.
If we do want to try to stretch the analogy, with the meetup-as-a-social-gathering being our city, then the asshole was breaking one of the city's ordinances - a social rule of not being an asshole who harasses others. Homeless and homeful alike would be arrested and fined, or put in jail, if they flung bricks through the windows; someone who's breaking social norms and making others feel unsafe ought to be expelled from the group.