The thing is that social/religious/ethnic/racial radicalization and extremism which endangered civil order, threatened civil debate, and came from places of willful ignorance, always existed prior to the internet. But it existed it pockets of time and place, and its spread was limited. Moreover, most ordinary uneducated people had no chance to post back to amplify its content, even if that content was spread on radio as in Rwanda or nazi Germany. Therefore the bulk of people whose opinions should never have had purchase had no sense that their opinions mattered. Which was a good thing.
Even more to the point, their inane debates (see: Fox News and MSNBC comments sections, Twitter, etc) wouldn't have generated advertising money. Their comments are not something that a sane civilization with a sense of self-preservation would wish to elevate to be seen by other people. The perversion of social media writ large is to make itself a Tribune of the People and compete with malevolent force of riot against protagonists of rhetoric. It is an insurgency in every sense of the word. Many of us who used to relish the idea of anarchist speech have realized that this insurgency is itself manipulated, that no free speech actually exists on these platforms but that they are simply used to whip the proletariat into frenzied riot on behalf of whoever controls them.
Not dissimilar to any religious cult that, in trying to attain power, allows its adherents to incite violence while simultaneously denying its own culpability.