I don't actually loathe the idea per se - giving every person in the household a room of one's own, if there's space for it, and it doesn't interfere with care of dependents, isn't inherently a bad idea. My dad had a workshop, mom had a craft room, us kids wandered in and out of both to learn, and if dad was doing something dangerous or mom was doing something she didn't need distractions they locked the door (I think mostly in both cases it was actually "making gifts for each other"). But if it works out to man gets man cave, woman gets kids and housework, that is a big nope. As this letter demonstrates, though, you don't need your own room for that - the problem there is less the mancave, more the manchild who dwells within.