Here's Shapira's video, documenting how he did it, as well as some of the German and English-language tweets which he reported.
In over 300 attempts to report hateful content to Twitter, the company responded just nine times. Shapira's view was: "...so I thought: OK, if Twitter forces me to see those things, then they'll have to see them too. These statements I reported weren't just plain insults or jokes, but absolutely serious threats of violence, homophobia, xenophobia, or Holocaust denial." The video comes with the hashtag #heytwitter, which others have taken to using in order to suppor Shapira's work.
If Twitter is slow to respond to hate speech, and it increasingly appears to have a problem in this area, then the company had better get a move on. The German parliament has approved a bill to fine companies up to €50m if they don't deal with the issue.