The claim "mainly due to its tolerance of anonymity" falls at the first hurdle (Wiley isn't anonymous), but it also makes little sense as a general observation. The "biggest transmitters of hate speech" are by definition the (non-anonymous) media with the biggest reach.
Twitter has about 330m users (some inactive, but that's the max auidence). Facebook has 2.5b & Instagram 1b. Aggregated, social media is thought to have a (deduplicated) audience of 3.6b. Newspapers reach 2.5b & TV about 5bn out of a global population of 7.5b.
TV is more regulated, but that's because it's more powerful. Social media, by its nature, dissipates. Indeed, it usually requires the amplification of press & TV to create an "outrage", as here. A bigot on TV or in a paper will have a far greater impact than anyone on Twitter.
Even if you think social media is pernicious, focusing on Twitter is odd. The reason it appears to rile so many is its anonymity, & that seems to be linked to weak consequentiality rather than a respect for bylines. In other words, ordinary people are "getting away with it".
