Just as if I were to post racist comments on my [Generic Social Media], my employer is going to need to do something to protect the company, because as the article points out: people (clients, customers) are judgemental, critics of gay marriage and critics of Brendan Eich included.
Executives of companies are representatives so much more than the rest of the employees.
I get that gay marriage is not an "arbitrary issue" for many people, but I think the definition of what is arbitrary and what are violations of fundamental civil rights can get tricky.
Like it or not, in the West, gay people are increasingly in the category of people who most people assume should have equal rights.
Whether being forced to resign as Mozilla's CEO counts as the community rejecting him is an interesting argument.
But there's a big difference (to me, at least) between being the CTO and the CEO. It's that step people are unhappy with.