Banning them stops them spreading this content on mainstream platforms and stops normal people falling in to the trap. It also makes the site tolerable.

Not everyone is as stupid as you're projecting them to be. You're in a bubble you created yourself.

I'm not really sure how this relates to the parent comment. On that original point, it seems crystal clear that a large chunk of the population is easily impressionable and can get quickly swept up in to batshit insane conspiracy theories and cults. There is no bubble here, we can see by the sheer number of supporters these conspiracy theories have that they are a very serious problem and we need to come up with solutions rather than going "Ah well it'll be alright"