What about fox news? AM radio? These are bastions of radicalization but they dont let anyone come on and say anything. At the end of the day this sort of rhetoric played by these groups is taught in university communications classes as a way to exert influence. Its all just propaganda at the end of the day, and that can come in the form of a pamphlet, or a meeting in a town hall, or from some talking head on tv, or a tweet. Social media is just another avenue for propaganda to manifest just like how the printing press is.