A few thoughts about why stars don't speak out sooner ...
(apart from a desire not to damage their own future prospects):
Not all these stars make a lot of money - some of the minor stars actually need the income from Conventions to keep them going, and even for those who don't, the residuals/royalties from the show are probably factored into their retirement planning.
So anyone thinking of complaining about their treatment by the show-runner might well decide not to, for fear of damaging the franchise, making it less attractive to fans, and the networks, and potentially depriving not just themselves, but their fellow actors, of an important income stream.
So it's good that they've decided to speak out, and we'd be doing them no favours by deserting the fandom, just because of one man.
Not all these stars make a lot of money - some of the minor stars actually need the income from Conventions to keep them going, and even for those who don't, the residuals/royalties from the show are probably factored into their retirement planning.
So anyone thinking of complaining about their treatment by the show-runner might well decide not to, for fear of damaging the franchise, making it less attractive to fans, and the networks, and potentially depriving not just themselves, but their fellow actors, of an important income stream.
So it's good that they've decided to speak out, and we'd be doing them no favours by deserting the fandom, just because of one man.