I'm no legal expert. Can anyone chime in and tell me if what he's alleging is even illegal? Seems like he's saying a bunch of advertisers got together and collectively agreed to not do business with Twitter anymore, ostensibly for a variety of reasons, but mainly because he lied about how their advertisements would never appear near hate speech.
That, to me, feels like something they should be well within their rights to do. A business can't just force other businesses to do business with them unless they're like under contract or something. But this doesn't seem to be a contract dispute unless I'm missing something.
There's the potential for a maybe-legit case here. Part of anti-trust laws include restrictions from competitors collaborating together, to gain some kind of advantage in the market. Price fixing would be a good example. A large group of advertisers collaborating on which clients they will or won't do business with does seem like it could fit the bill.
My guess is it'll come down to WHY they singled out Twitter for blacklisting. Does it give these advertisers some advantage over competitors in the market? Or allow them to exploit consumers in some way? Or is it maybe because the CEO of the company made false promises, and then publicly told them to go fuck themselves?