This is too weak. His politics don't matter, period, unless he brings them into the office himself.
But, following this comparison, what if this hypothetical racist had an established work history of not letting his/her racial opinions impact management? Eich founded Mozilla and likely had a great deal of influence on the its culture. Yet he did nothing I've heard of to impede Mozilla's organizations from embracing diversity in all forms.
I would still feel very uncomfortable working at such a company, and I think that's the sort of environment Mozilla wanted to avoid.
"what if this hypothetical racist had an established work history of not letting his/her racial opinions impact management?"
I'm not sure that's possible (bias creeps into just about everything we do-- and this is a pretty strong bias). Is it possible for someone with these views to not have them creep into promotion discussions, pay raises, meeting invites, tone in emails? Even if it is, having an opinion that is abhorrent to a majority of your potential hires, partners, reporters, and customers makes it pretty hard to lead.
I stand by my original statement.
EDITED to add: after all, if you're right that he would have been unable to keep his prejudice out of the office, you wouldn't have had to wait very long before he screwed up in some way, and then he could have been fired with real cause.