Yes. I believe that David Leip has every right to ban me with or without reason. It's his forum. Likewise, free speech doesn't apply in other people's homes. I can't go upstairs to my friend Georges apartments, insult him, and not expect my speech to be protected.
So would the OP be ok with salafi muslims and trigglypuff holding occupy protests on sunday morning inside whatever christian church they come across.
Both this. Functionally the First Amendment doesn't work in practice inside private forums that have no government funding. The owners of private spaces have every right to do with it as they please within accepted current constitutional and legal statutes.
I don't understand your slow conversion into a 1970s liberal.