you left off this part of the quote, it changes the meaning completely, what does it mean to have evil desires? what is the cost of a)having them, and b) acting on them? If a person ponders these further questions and then still chooses to act out their evil desires then they are irrational, but the study of them, which I would wager most "evil-doers" do not do (ponder, study their own desires), she is claiming to be the highest virtue. This is what Christians do through prayer, and others through other forms of meditation.
You're wrong. Stalin and Mao were quite rational and logical and clear-headed (much more than most people) and considered themselves overwhelming successes. It just didn't matter to them that they wiped out tens of millinos of people; it made rational sense for them to do such to reach their goals. That we consider wiping out so many people evil comes from somewhere else.
Christians are told by God and Jesus what is wrong and what it right. It's then up to them to obey or not. When they have desires (as they all do) to do bad things, they know immediately that such is bad (they've been told so), and they know there will be a price to pay for behaving that way.