Did they actively remove it, or did it just age out of trending like everything does after a relatively short amount of time?
Twitter's actions aren't even self-consistent here. If these tweets were all innocuous, then why remove the trend? If they were primarily discussions of other people's activity, rather than explicit calls for violence, then there was no good reason to do this.
Also, there's nothing "moving goal posts" about asking people to at least try to substantiate what they post. The person I responded to didn't even bother posting a link.