Yeah, you shouldn't have to tank if you don't want to. If your guild starts to harass you, leave.
You're not being selfish by not wanting to tank. Everyone has some role they prefer not to do (personally, I dislike dps'ing).
^This. Play the roles you enjoy, and if there are not enough people around that enjoy tanking, well then measures would need to be taken to make tanking a more rewarding and enjoyable experience.