If you have at least some of your militia train in your primary meeting area, it seems that dwarves milling about there will gain a little bit of discipline skill. They'll still get bad thoughts from seeing the corpses of sapient beings, but they'll haul 'em anyway.
Need to be careful with that. I had a child's head explode after a collision with the largest dwarf in my military.
Never had that, lips, ears and such "splitting into gore" happened quite often, but nothing more serious. Then again, I only use ramps for the main part of the fortress. If I had stairs go right through the dining hall like I have ramps, I'd have had many fatalities I guess.
Only time I had lots of hurt dwarves was before I set the tracks for the minecarts to "restricted traffic". Somehow dwarves love to stop pushing minecarts halfway along the track, causing them to go down their ramps out of control...Since I changed it to restricted everywhere where the minecarts can derail I tend to only lose peregrine falcons every now and then. Though since most of the times the minecarts weren't deadly (using wooden minecarts), at least my medical dwarves were getting some training. Buuut...earlier in the fortress I did lose two dwarves to it, one of them a child.
There are some weird behaviour things about sparring causing teleportation from what I heard though, but I feel like these small problems outweigh the use one gets out of having every dwarf be a legendary observer and not freak out at the slightest sight of a dead being. Just...don't have stairs in the dining hall/training room. And don't have a 1-wide wall bordering on a deep pit as the room's walls. Hm...then again, thinking about it, I never had a dwarf teleport into my well's water supply which is only seperated by a 1-wide wall from the dining hall/training room. I did have one dwarf magically smash into the wall of the ravine in which my river runs though. Still no idea how he got there or what happened there.
But yeah...whatever it is, something causes my dwarves to rarely ever feel horrified. Either the training in the dining hall, or the massive amounts of corpses they already had to haul away.