The problem I have is that almost every recruiter that emails me lists the positions they are trying to fill. Almost all of those positions are ones to which I am morally opposed. It's a waste of both of our time to respond positively and interview for positions that I won't accept under any realistic circumstance.
I'm not sure how you go from "Never ignore a recruiter" to "Always respond positively and interview with a recruiter". There is a middle-ground where you can reply, without being positive and not setting up an interview, while not burning bridges that you might want to cross in the future.
