Color me skeptical. Padmapper is a for profit business, and Craiglist ads make up a huge fraction of all online housing listings. In the absence of any explanation at all, I hope it's understandable why I wouldn't just take your word on it.
In any case, I agree with others that you don't need to bring these kind of justifications to bear. Craigslist has no right (either legally or morally) to facts about rental locations.
As someone that knows Eric personally, I can confirm that he'll make less money by showing craigslist listings. However, I'll leave the details up to him, though I understand why without them, you're skeptical.
PadMapper is actually a pretty unusual "business" since I'm the only person who works on it full time and it grew out of a hobby project, and still isn't really run like a business. But yeah, that's generally a reasonable assumption.
I don't have to, but I thought it'd help to explain my reasoning to people.
In any case, I agree with others that you don't need to bring these kind of justifications to bear. Craigslist has no right (either legally or morally) to facts about rental locations.