As has been said before, it's a race to the bottom--other countries will do it, so we better get a piece of the action.
If it makes you sleep better at night, as portrayed in "Lord of War", the Russians were happy to sell their weapons to countries who then armed child soldiers. We on the other hand, arm nations, who then have the luxury of dropping laser guided bombs on children instead (or merely maintaining a grip on power, whatever. Insert all ethical 'gray area' actions here, of whatever nation).
Point being, you should quit bothering about it. You entered the military-industrial complex the day you were born, like most citizens of modern industrial nations. Have you ever looked at the projects your local university receives funding for? The families of companies your parents or relatives work for?
In the long view, we're little better or worse than anyone else. Get off the computer and go find three things:
1) money
2) pussy
3) beer
There. I just saved you a lot of heartache.