From my perspective, I don't want to work in an environment where people are voicing their opinion that (e.g.) gay marriage is illegitimate or wrong. How am I supposed to work with someone who thinks a huge part of my life is immoral? I would have an incredibly hard time believing that that person was taking me seriously, really wanted to work with me, wasn't going to undercut me, or trusted me.
It's not that you can't have these opinions or voice them -- but it's also not the case that the people who are most affected by those opinions are going to feel OK about it.
It's not that you can't have these opinions or voice them -- but it's also not the case that the people who are most affected by those opinions are going to feel OK about it.