I think it's offensive. Imagine if we had a phrase called "womansplaning" to describe someone who sounds uneducated about the subject they're explaining, Would that be ok?
The point of the term (as I understand it) is the situation where someone one in the majority explains something to someone in a minority that that person already knows, possibly quite a bit better, ending up bro condescending while possibly trying to be helpful.
Since that seems to be a very frequent occurrence for men to do to women (relative to the reverse) it seems fair to me.
Let's take a different context. When southern white racists would explain to African Americans in the south how they were well treated and free after the civil war (say the 1930s) would a term like 'whitesplaining' not fit?
:) No worries. I personally don't like the term because I'm a man who is quite capable of explaining things well. Most of the things I see labelled as mansplaining I think are poor explanations that lack nuance, introspection, and social / emotional awareness, and as you pointed out they are usually condescending. But how does it relate to my own manhood when something someone else writes is labelled as mansplaining, since I've also been attacked due to my membership in the class? Am I not a real man because I'm not lacking in these things? No, of course not. Would I be offended if some angry person labelled my own writing as mansplaining? Not really, they'd have to attack me on the specifics, in which case I'd listen, etc. I would however use it as a filter indicating I should be wary of their future arguments though, just as I use other slurs as a filter.
In general I think it's pointlessly divisive to invent slurs for the other side in the push for egality. That said, men probably have 10x the number of slurs for women (at least if our names for genitals is an indication), so it does make for an uncomfortable object lesson.
