However, all it takes is a change of framing - step away from the "people" and look at the "justified". If your violence is justified, then the issue goes away.
And, really, it doesn't take all that much work. You want your players to have a good time slaying orcs? Sure - just put in the scenario setup that the orcs in question have been doing heinous things to local villages, and there's evidence to say they'll continue. Presto! Instant justification! With a few sentences of exposition, justification can be done.
The issue comes up when you present things that aren't covered by justification - just don't drop in orcs who haven't done anything yet.