I think it's the hypocrisy issue.

It's like politicians. If regular Joe politician cheats on his wife... eh, that's between him and his wife, none of my business.

If Ultra-Conservative politician who has been banging on about the sanctity of marriage and trying to dictate what I can do with my love life gets caught shagging his secretary, then it's very much my business - because he involved himself in my business, and he set standards of behaviour for me and then didn't live up to them himself.

So if Jane Average does something wrong, then that's bad. But if Jane Social Justice who has been telling everyone else how to live their lives does something, then it seems worse, because she the one who set the standards for what's allowed and what's not.