https://www.theguardian.com/technology/2017/aug/08/artist-protests-twitter-inaction-on-hate-speech

Shahak Shapira and other artist-activists stencil insulting barbs to protest what they deem the company’s muteness on offensive tweets

A German-Israeli artist who accuses Twitter of failing to delete hate speech tweets has taken matters into his own hands, by stencilling the offending messages on the road in front of the company’s Hamburg headquarters.