Hey, Evulz is a pragmatist. His society is set up around doing the extreme that needs to be done, for which most view him as evil, but he's by no means going to do anything negative just for the hell of it.
Evulz appears to being ready to spare the people of Cort, then slaughters them
Evulz really was doing it for pragmatic reasons, but eventually realized that playing the part of Noble Demon would give him more leverage and decided to pretend his "real" reasons were moral all along.
Slaughtering the people of Cort was an idea of one of Evulz's Stupid Evil subordinates, whom Evulz executes.
Parodied: Evulz never actually does anything evil at all, and in fact donates regularly to charity and helps old ladies cross the street, but keeps up with the Evil Gloating as he does so, gleefully pointing out to anyone who will listen how these acts of kindness totally furthers his evil goals.
Zig Zagged: It's hard to tell whether or not Evulz is acting out of pragmatism or genuine goodness, with plenty of evidence for both.