You are missing the point. Organizing, coordinating, recruiting, all these activities have costs associated with them. Costs like time spent on them, time spent finding tools to use for the job, etc. Make a racist subreddit go away and the N people who were a part of it won’t stop being racist. But it will be harder for them to find another platform to recruit and to some degree harder to find ways to coordinate. Now time that could have been spent indoctrinating new recruits can is being spent on less productive tasks, slowing the whole community down. Will it stop racism or even the racist group from doing what they do? Of course not. Will it slow them down, yes absolutely.
If a bunch of assholes showed up to your front lawn and started doing asshole things, do you kick them out knowing that they might go to your neighbor’s lawn? Or do you keep them on yours to protect your neighbor? I guarantee you that you’ll kick them out and then likely help your neighbor kick them out too, not shelter them and help them do the asshole things by providing your lawn as a platform. How is this different?