That’s hilarious, anomander 
You know, it’s funny. I’ve never noticed that manspreader thing. Part of it may be that I generally fly first class, or at the least, have an exit row or economy comfort seat, though that may not give you a wider seat, just more leg room in front. I also tend to keep my legs directly in front of me, or crossed, so I don’t take that much space. If it bothered me, I’d probably pull out my flight bag, and put it into that space. I don’t know if that would work, if someone is particularly aggressive, however. I’ll have to watch for that.