"Doesn't care about anything anymore" is the result of witnessing death a lot, correct? From what I've read it makes it so that when someone dies the dwarf is not negatively effected. I understand butchers, soldiers and hunters get "witnessed death" in their mood if they have killed something, but is it possible to get it when something dies nearby?
Also, isn't the main cause of depression/tantruming the death of loved ones?
Here is what I propose! Expose your populous to death. Lots of death. So much death that they all no longer care about anything anymore. Half of your mining team can cook in magma and no one will so much as blink an eye!
At first I was thinking it should simply be a matter of locking them into a room with bred wild animals and setting them to hunt. This leaves too much to chance, however.
Instead I'm thinking of mass pittings down multiple z levels, the bottom of which is a room full of dwarves. Perhaps half the fort can be locked in there while the other half pits.
Because of my experiments with dwarven drop pods I know that animals and dwarves falling directly on other creatures do not get harmed so the landing zone for these animals should remain clear some how. Obviously if the dwarves are locked in there they will not attempt to haul the bones and gore created in the process.... can you zone an area in the middle of a room so that dwarves do not walk there?
Anyway, a few hundred dogs or so and I figure mothers will be unfazed by their babies being consumed by orcs...
Perhaps when you get new waves of immigrants they can be hurded into this room and indoctrinated.
(edited to clarify)