The response to that would be that you only do things that give others pleasure because the feeling of helping others is pleasurable to you or because you expect something in return, and that if neither of those were the case, you wouldn't do it. (I don't necessarily agree with that — I'm pretty sure I don't — but I do believe that's how they'd reduce it.)
This is our monthly thread for collecting these little gems and pearls of wisdom, rationality-related quotes you've seen recently, or had stored in your quotesfile for ages, and which might be handy to link to in one of our discussions.