Heh... I've used insults 3 times so far, after I got my entrance/exit traps finished.
First was ~1500 sent, they showed up immediately after my 'Ambassador' returned (1 game minute... poor guy got to move one step towards safety before dying). Final tally of corpses was 41 goblins and 11 ogres. May have been more, I had some crossbowgnomes wounding them before the trap lever got pulled, and I think a few ran off bleeding.
Turned them all to sausage, and sent everything on the list except the two headed hide to them. Came in around ~10500, I think. Same thing on the return for my poor gnome, 1 step and dead. 411 goblins, 100 or so ogres. I remembered to turn off my butcher before collecting the bodies, and I've got a fun screenshot (and backup save) of all them surrounding the corpse of my dead 'volunteer'. The pile of worn armor filled up my smelting stockpile, and a 32x64 space besides.
Hubris got the best of me, though, when I butchered the lot, left the skulls uncarved, and sent off ~110000 this time. A regular raid came in before my Insulter got back, so he lived... and then a few days later the retribution came. The lag brought my (pretty beefy) computer to its knees... sigh for no multithreading. After noting the arrival time and going to a backup save, I optimized everything for the arrival - got all my gnomes unarmed so no one was shooting , stationed at single square guard posts underground, no actions going on, and 8(!) lever pullers ready to rush. Killed the raid in one go. No idea how many were there, though; the lag was so bad that I got the wall down and path opened up to the bodies, but could deal 1 frame every 3 seconds anymore. I'm guessing 5000+ guys, with all their equipment too