Jen
I am probably one of those whom you refer to who has a bit of a tendency to take the moral high ground so to speak. I acknowledge the criticism, it is fair and perhaps at times I have been overzealous in my advocacy of full disclosure.
I think you are right in that BOTH telling and not telling can have selfish elements. There are also unselfish reasons for both telling and not telling. My advocacy is that if you are NOT telling then please make sure it is not for selfish reasons but for unselfish reasons.
The major problem that I have with NOT telling is that you deny your partner choice. The choice to learn about it and decide for themselves if it is something that concerns them. It's a sort of free will argument. Some may choose to not want to know (pretty much what DADT is really) and some may choose to know more. The key for me is that they get to choose, not us trying to decide what is best for them.
Overall I think you are right. The benefits for us in telling should be to a certain extent a side effect, i.e. feeling good about being honest etc. In the same way that I said if you are not telling make sure it is for unselfish reasons, I would also say if you do tell also make sure it is for unselfish reasons, not because you hope to gain something.