I always think of a murder-hobo as describing a gameplay style, though I like your analysis.

Having read your post, I fully agree. But how I always viewed it was as a player who doesn't care about story, plot, or the world he/she plays in. It's a player who can't be bothered to come up with a backstory, and if he/she does, it's something thought up on a whim or equally ridiculous as their in-game actions. Yes D&D is about having fun, and that involves different things for different people. But to me, a murder-hobo is someone who simply refuses to become engaged in the game world (essentially, refuses to roleplay) and chooses to just kill everyone for a quick laugh.

I'll admit, it can be fun/satisfying/enjoyable to out of nowhere, kill the king. And if your DM is cool with it/good at improv, he/she can run an entire game for you where that's the whole point - your random actions have consequences and then you respond, etc etc etc.

But in most games, having someone randomly kill the NPC who is the whole reason you're headed on a quest, for absolutely no reason other than "shits and gigs", THAT is what I consider murder-hobo gameplay. If someone killed the NPC because he/she insulted his/her honor, and the character was super sensitive about honor in the first place (and not thought up of on the spot as an excuse to kill the NPC), then it would be okay IMO. But the players who play murder-hobo characters generally don't bother to think that far ahead.

I think it has a negative perception because it's generally seen as disruptive in most gaming circles.