I assume since we're beyond first level, we've done more than our fair share of adventuring thus far. Outsiders are very iconic, and I'd imagine that by this level he's faced more than a few of them. They are, by definition, Evil (with a capital "E") incarnate. While he's not a paladin class wise, he's pretty close to one--Crusaders are Paladins without the necessity of a code of conduct. He can make decisions, when they're of absolute necessity, to work with Evil creatures and won't fall due to it, but far and wide unless he's forced to be circumstance, he prefers to smite them due to the danger they pose of affecting and corrupting the people around them simply by their presence and influence. It's not mindlessly butchering them on sight; it's ending their ability to corrupt people and inflict pain and misery on good, decent people. And as you said, non-evil succubi are vanishingly rare. I don't think it would be unsafe to assume that outsiders with the Evil subtype are Evil, especially with how convincing and seductive some of them can appear.<br/><br/>Plus, you don't have to take levels in Paladin to be a Paladin (http://www.giantitp.com/comics/oots0209.html) :P<br/><br/>Also, is the summoned succubus an actual cohort, or simply a bound outsider?