Sure, the actual group won't stop existing if you ban them

Honestly, I disagree with this. These communities are, at a fundamental level, unstable. Their simultaneous reliance on powerful authority figures and their inherent distrust of authority means that, without a community which is carefully directed, they quickly fall into infighting. We have seen this several times on T_D, where Trump makes comments against their general beliefs (like that time he was pro-gun control for about 24 hours) and their community almost immediately started fighting amongst itself until the mods moved in a wiped out the dissent. A major ban wave which features their communities, sends some people back into saner parts of the web and allows others to compete to be the new captain of the ship will result in a community that can no longer coax new membership into their ranks, while also can't decide what it is they actually stand for anymore. Breaking up these groups would result in a massive collapse in their support.