No. Anyone should be able to support any political cause at any time.
In a free society, we do not rely on force to produce morally correct behavior, except by force of state. We rely on law instead, which conversely requires complete freedom to participate in the democratic apparatus. Anything that messes with that messes with the very heart of a liberal democracy.
Corporations do not have unlimited freedom of association anyways. For instance, we already acknowledge that corporations can't refuse to associate with people on the basis of skin color. Saying that they could, say, fire a black CEO because otherwise their KKK customers would walk out, already doesn't fly; I don't see why it should have with Eich. I think racial equality is important, but political neutrality is at least equally important, because if that fails then liberalism is fucked, and liberalism is the best guarantor of racial equality as well.
Mozilla employees, volunteers, and others used their freedom of speech to say they would exercise their freedom to dissociate from Eich if he continued to support discrimination. Eich dissociated himself from Mozilla so the others wouldn't.
Okay, let me explain that one. I know he says that, and I know Mozilla says that, but "I've decided to leave of my own accord" has simply become such a cliche that it can no longer be distinguished from firing.
In any case, this mostly just supports my view that people don't understand liberalism and why we need it. When an atheist and a christian can sit down together and have a peaceful family dinner without talking about politics, despite the fact that at least one of them thinks that it's a matter of utmost moral importance that the other change his mind, this is a miracle of social cohesion that is crucial to keeping society together. And we're losing it.
In a free society, we do not rely on force to produce morally correct behavior, except by force of state. We rely on law instead, which conversely requires complete freedom to participate in the democratic apparatus. Anything that messes with that messes with the very heart of a liberal democracy.