The pseudo-gotcha about tolerance is ridiculous, an accusation of hypocrisy based on a straw man. Gay marriage isn't about some mushy notion of tolerance. It's about civil rights, about equality before the law. As you point out, we don't yet know his views. This is about his actions.
And the concern about him as CEO also isn't about tolerance. It's about safety. Given that Eich has worked against the civil rights of gay people without explanation or apology, it's reasonable for gay employees and business partners to be concerned. When he was CTO, it wasn't as big a deal, because that was a technical role. But as boss of everybody, it's a different thing.
Personally, I don't think he should have left over his donation. I think he should have explained and apologized for his gay-hostile action before or as part of the CEO transition. Failing to recognize the problem in advance and then failing to deal with it quickly and forthrightly did make me strongly question his fitness to be CEO. Mozilla's CEO needs to lead and inspire people, and to adroitly handle the media, both traditional and social, adroitly. At that, so far, he's very much failed.