They can't stop anything. Incels aren't a movement, it's just a sentiment of men who aren't getting any sex and relationships, and there's increasingly more of such men every day in the West. Until these men get satisfied in some way, these opinions will continue to float the internet in one way or another.
Even if they ban all the explicitely incel sites, incel opinions will simply infiltrate the closest next thing.
I think this is what ultimately bothers them so much about this whole phenomenon. It's a nasty product of the society they support and that they depend on and they wish they could just ignore it and pretend it doesn't exist.