In any case, I confess I'm always a little suspicious of this method of argument. Bob says, "I will ban neo-Nazis from my forum," and people chime in with, "Well, what about banning Catholics? Vegetarians? People who admit to liking Nickelback?". Is the principle really that if we find one single case where Bob would admit "I don't think banning that group makes any sense," then Bob needs to just give up and let neo-Nazis on his forum? Personally, I don't think that's a very good principle. An argument about where we (and Bob) should draw the line is reasonable, but I'm not convinced an argument about whether lines are intrinsically evil is.
I don't think many people would argue that we need a forum where people can advocate for pedophilia and child porn. We've clearly decided that sort of thing is bad. But saying we're going to ban child porn is not the same thing as saying we're going to ban vegetarians.
Certainly reasonable people can disagree on what types ideas deserve platforms. I imagine some (misguided but well-intentioned) people might think that providing neo-Nazis a platform to advocate for their position is a good and fair thing to do, even if they disagree with the neo-Nazi message. But it doesn't mean that people who don't think that's ok are somehow anti-free-speech fascist dictators who want to have control over every kind of speech.
I also get exhausted when people trot out the slippery-slope argument at every opportunity in order to shut down discussion. Not everything has to be a slippery slope! People are actually capable of making decisions in a nuanced, fine-grained way!
Catholicism is an organization that as one of its main tenets is homophobic. How is that better (or is it worse) than being an Confederate flag-waver or a neo-Nazi or a Black racial separatist or ? I'm sure the answer is obvious to you, but only because of your personal idiosyncratic preferences. Evil is not an objective spectrum. It's a subjective high dimensional manifold.