I understand your frustration. If I had been in your shoes, I would've not engaged with this person, and simply logged out to switch servers. They're looking to get a rise out of you, and if you don't engage, you ruin their fun.
-Spawn-camping limits wouldn't work for a game like this. If you couldn't kill each other, what's left to do, stand there and wait? How would this work on ships/in hourglass, etc.?
-Treasuries only have 1 small "safe" room you respawn in. Having other locations in this small room, wouldn't work. You also can't spawn inside the treasury, in case you're fighting underwater and now spawning there (and risking black screens) would be a nightmare.
-This has the ability to be abused.
-You call them jerks, when they're just doing what the game allows them to do. In my opinion, this person was rather foolish, as he should've waited for you on your ship to collect your treasure first, but got impatient, and decided to TDM you instead.
You're so upset by this person interrupting your attempt to get treasure. Imagine if you had completed the treasury, was harpooning your loot, and suddenly you're dead and they come around and sink you? I've had that happen to me one time before I learned better tactics.