Perhaps the reasons why those groups grow so easily should be addressed instead of treating it like it is an inevitable force of nature that can have a dam placed in the right spot to keep it eternally contained.
But it should be obvious given the last decade or so, if you've been living above a rock, that the internet and social media provide a force multiplier for speech that, due to the priorities and incentives of algorithms, prioritizes speech many might consider harmful and dangerous. One can no longer naively accept truisms such as "sunlight is the best disinfectant" and "the only answer to bad speech is good speech" when history has shown that the playing field is not level, and that despite being exposed to the light of day, running riot across the internet and being debated furously on all fronts, these groups only feed upon, harness and grow amidst the controversy and chaos. However, limiting the scope and velocity by which they can spread their message and recruit has proven effective in slowing their influence, if not stopping them altogether.
You're also presenting a false dichotomy here. We don't have to choose between restricting hate speech and fighting hate groups on other fronts, we can do both. However, just as one does not deprogram a victim from within a cult, one cannot effectively address the root cause of the spread of racism and hate in an environment where that message spreads unabated.
"Those who do not remember the past are condemned to repeat it," indeed.