Just to expand on Sg's points a bit...

Freespool's 10% mortality figure may well be accurate for all I know, but a large portion of that percentage is likely due to inexperienced or otherwise poor fish handlers keeping fish out of the water too long or injuring them, despite their best intentions. I'm not trying to belittle the significance of that 10% (as many have said, most fisheries can scarcely tolerate even that level of mortality), but I'm trying to point out, without getting into too many details, that experienced CNR anglers probably don't kill one in ten steelhead they release. Even if they did, they would still be doing only 10% of the harm to the species that someone who bonks everything he catches does, and that should be worth something, IMO.

As for the ego thing, although I don't mind eating them (and will when they are of hatchery origin), I don't ever take pleasure in killing fish. Personally, it does my ego a lot more good to watch a prime specimen (8/18+ pounds - who cares?) kick out of my light grasp and return to the river, where my hope is that I might have the thrill of encountering one of his or her offspring 2-4 years later. It does the heart good, even if it occasionally takes a toll.