Promoting defection also makes sense in situations where being seen to promote defection rather than cooperation earns me status within the community (e.g., it seems cool, or seems clever, or seems contrarian, or what-have-you), and I believe that promoting defection does not significantly affect utility otherwise (e.g., I don't believe that anyone I care about might ever be in a prisoner's dilemma where the results actually depend in any way on the stuff I promote now).