They weren’t, it was just the example at the furthest end of the spectrum. But your framing of “if it was REALLY bad, Twitter would ban it” can not be the solution. We have legitimate governments tasked with governing based on the will of the people, it’s not better to just let Elon Musk or Mark Zuckerberg decide the law.
They would ban it if was really bad because it’s illegal for that stuff to exist and they will face much more serious issues as a company if they don’t remove it, they’re not doing it out of the goodness of they’re hearts
Also not a good look for a company to be hosting that stuff in general for their PR, which is determined entirely by the general population’s reaction to their actions and not a small group of individuals in powerful positions