I think Wesley's decision stank of self-righteousness. He got one friend expelled from Starfleet and made life for himself and the other two extremely difficult and tarnished their careers all so he could say he kept his precious principles.
I don't see how it's self-righteous to own up to your mistakes, especially mistakes that got one of your friends killed. To say "I'll lie about what happened to my one friend to cover my other lying friends' asses," seems a bit hypocritical and certainly not very friendly to the dead one.
I believe the word you were looking for is "mature", not "self-righteous."
That said, if you're willing to throw one of your friends' good names under the bus to save others...well, remind me not to be friends with you if there are any buses around.