If you were talking about Eich, he should be free as a private citizen to support the political causes he chooses to, even if those causes are disagreeable. He did not interfere with gay members of the Mozilla community, nor make his anti-gay-marriage contributions in a capacity of representing the Mozilla Foundation. He was literally as low-key about it as he could possibly be.
It must be nice to imagine the rules of society don’t apply to you, but eventually society disagrees. If you are bad at your job, you might be fired from it, and “not making the entire industry a more hostile place” was at last part of the job description of an MIT professor.
Also note that there are actual laws about it in the USA, so not only is it part of the job description, it is a legally required part of the job description.
And even if he were opposed to gay marriage, if you cannot imagine how someone can philosophically oppose something, even if they are wrong, and yet still practice tolerance for that thing in their own life, then you cannot be reasoned with and should probably delete your account.