For me, I like the idea of a weapon with history, but I'm also a little icked out by the fact that my rifle may have/is likely to have been manufactured using slave labor, or in the case of some, to have been used in mass executions. Ditto surplus ammo. Of course, this is all theoretical, since I don't own any milsurps yet, but I plan to shortly.
Won't stop me owning them; it's not like I'm encouraging slavery--the people and systems involved are pretty much dead and gone--and it's just an object, neither good nor evil, just fun and useful.
Still, I don't like to think about it too much. Or maybe I do, but I like to think that using it for target practice somehow redeems it, gives it a better use. Nothing wrong with a battle rifle being used to kill people in battle, and I'm cool with that, but weapons have been put to much more nefarious uses including some (weapons that is) tat might end up in my hands.