“This is not to say that exposure to a virtual extremist community drives one to offline violence. Social media is only one contributing factor and likely does not substantially alter an individual’s propensity for violence. For some, the ability to find and interact with extremist communities online is an outlet for nonphysical expression. … Even though mainstream platforms may maintain and enforce content regulations more aggressively, the sheer volume of content hosted on these platforms—combined with the scale of their user base—means that they possess, in absolute terms, substantially more toxic and hateful material than fringe and niche platforms.”
https://www.rand.org/content/dam/rand/pubs/testimonies/CTA1400/CTA1458-1/RAND_CTA1458-1.pdf