I want to believe that it's a combination of (a) the sheer volume of tweets that makes it impossible to catch all the stuff and (b) that there's probably a lot

I want to believe that it's a combination of (a) the sheer volume of tweets that makes it impossible to catch all the stuff and (b) that there's probably a lot of overlap (at least initially) between people who read the tweet and people who agreed with it (so a relatively small number of people flagging it as a TOS violation).