Are people actually using the phrase, "Get over it!"?
I have not actually seen 'get over it', but I have seen some very blunt phrasing, and the ever-present 'this wouldn;t be my hill to die on' which I think is a bit PA.
I disagree, quite strongly, that that expression is PA. There's a lot of misunderstanding about what passive-aggressive really is on this board. PA is saying one thing (a passive statement) when you want to force some response from someone else (an aggressive action.) Someone's MIL saying "Gee, it's really hot in here" when she means to say "could you please get me a drink of water" is PA.
That said, I don't find anything wrong with the "that wouldn't be my hill to die on" to be out of line at all. It's expressing the feeling of that particular poster that the issue under discussion wouldn't be as significant is it is to another. It isn't telling the other person that they're wrong for feeling that way, but that the poster doesn't. It's no more out of line than someone saying "I love carrots" in response to another poster saying "carrots are the most evil food in the universe."
If someone just wants validation for their feelings, then this isn't the forum for them. People come here for advice and they get it -- not always the advice they want, though. They get other perspectives, which may help them look at their situation in a different light. I, for one, appreciate
hearing "that's not my hill to die on," because it helps me look at my situation with fresh eyes. If all I wanted to hear was "you're right; that stinks, go out and give 'em hell," I'd talk to my mirror.