In war films and WW2 RPGs we don't worry if the soldiers you are fighting are inherently evil or not, they are the enemy and the situation often demands violent action.
Why do orcs need to be inherently evil for us to avoid feeling guilt over slaughtering them?
I'm sure a lot of the people who protest about inherently evil orcs are absolutely fine with the "Punch a Nazi" statement, when we know Nazi's are real people and therefore possibly capable of redemption. Why moralise of killing orcs (inherently evil or not), when we don't moralise over killing enemy soldiers, stormtroopers, terrorists, etc in other settings, or punching Nazi's in real life?