I think @peachfront was talking historically, the KKK et al have existed for decades. Social media is just a new tool to them to recruit new members. Only that is also helped by right wing media, possibly poor or lack of education and of course upbringing.
In the UK many of these groups are banned, membership and association included. They can't generally use free speech to justify their actions. I think people have said here on fedi that after WWII many countries quite rightly banned association with NAZIs and their thinking, while the USA didn't, perhaps citing the beloved first amendment and that has led to the issues we see today.
Something has to change, does the first amendment or free speech have limitations or is it a free for all to say what you want with impunity and people just tolerate it as if it is normal?