Sensible Archangels tell their Malakim something like, "I order you to avoid killing humans, even evil ones, unless there is no other reasonable option."
This means that if they leave an evil human alone, it's not their choice, and so they do not get dissonance -- but there's enough wiggle-room for heat-of-battle and the like.
Evil ethereals are just as much target practice as demons.
Of course, "evil" can be a slippery concept, even for the Malakite resonance. And there's the tack Novalis prefers her Virtues take, which tends to be very much in the "hate the sin, redeem the sinner" line. Destiny's Malakim are similarly prone to "Best way to kill evil demons is to get them to be good angels" thinking.
And then there's Kathriel...
http://www.sjgames.com/pyramid/sample.html?id=894 (Not canon, but, whuzza term, deuterocanonical?)