Why doesn't Twitter have something like WordPress's Akismet? Akismet is a plugin that filters spam by combining information about spam captured on all participating sites. It uses that information to generate rules to block future spam. I know that bad actors can easily create new Twitter accounts, but should also be easy for a large group of people to tag them in real time.
And I'd imagine if you can create an algorithm that can predict what you'd like to buy, surely an algorithm could be created to identify both hate speech and the speaker based on a few online real-time gestures. Identifying these storms of attacks, like the ones against Leslie Jones, is not too different from identifying the events that Twitter wants to sell advertising against.
Twitter valued being unfiltered at a certain point, but now the stream is quite polluted.