So he couldn't support a gun lobby and keep his job; or support abortion and keep his job (assuming there are some people in Mozilla who oppose guns/abortion)?
you just cannot compare those to gay rights. Neither of those perpetuate inequality or hate. In fact they are in support of individuals rights.
being against gay marriage is wanting to strip people of their rights and promote inequality. It is like saying only white people can get married, and if that was the case how would you feel about it then?