> How did the UK get a point where planning terrorism and making mean comments online go into the same statistic for arrests?

In most publications: because the people reporting on these statistics can get more views and clicks that way. FUD sells. If someone online can defuse the statistics, the reporters that spread them also could've, but chose not to.

As for the second half of the list, "racist abuse, hate speech, and unwanted communication" are pretty common things to incriminate. Even the extremely liberal freedom of speech laws in the USA do not permit stalking ("unwanted communication") and racist abuse is criminalized in all kinds of cases (i.e. firing someone because of their race).