No fan of gt, but anyone who fished the first few seasons of wild coho release remembers how difficult it was to find clipped fish. I had close to zero bleeders with casting flies, but saw tons of floaters released by those fishing gear, especially double hook rigs. Everyone who fished those years thought exactly how gt did. Many acted on those thoughts and as someone who experienced it I cannot get too moral against those who did... although changing gear types would have dramatically reduced bleeders and mortality, which most fishermen refused to do... so I guess I can get a bit moralistic
I agree in general that fly fishing barbless hooks is less likely to cause harm to mature coho. I do wonder often about the impact of fly fisherman on smaller fish though. I tend to catch a ton more shakers than gear guys, especially herring guys which makes me think I am having as big an impact or bigger on overall coho populations (assuming a certain % die after release). Might, just be me. Maybe I am the shaker king but it seems that way with other fly guys I fish next to as well.
In the end though, breaking rules just leads to more rules and less opportunity. Plus just because you did not get to eat it, does not mean it goes to waste. Lots of things depend on coho in the sound.