Free Speech isn't dangerous, but censoring one side of the argument is, and that's what's been going on for years and still and most popular platforms. From the left wing perspective Twitter probably appears to support free speech.
Still plenty of right-wing voices on Twitter and on numerous other platforms with millions of viewers... it's also for the most part only censorship if the state itself is involved.
Twitter removing someone when they've abused their platform for which they have zero right to is an entirely justifiable act, it neither stops them from seeking other platforms or investing in new ones which is what is meant to happen in our supposedly capitalistic society.