the US military should open fire on people on American soil
Sorry but that is shoddy reporting. The tweet did not say that and misrepresenting it like that demonstrates that The Register is putting clicks ahead of accuracy; a woeful lack of integrity and demeaning the journalistic credibility of the entire site.
Twitter hasn't taken action against people that actually are glorifying violence, by supporting or even encouraging the riots and looting; claiming that the tweet in question is in breach of their glorifying violence rules is a clearly political act in itself. Their choice, but The Register should not be joining them, let alone creating its own false news.