I really don't know if using having barbs on the hook really cause that much harm to the fish. I suppose it may depend on the size of the hook and the fish.
I do think the ease in which a barbless or hook or one with the barb crushed down comes out aids in speedily releasing the trout which certainly aids in the trouts recovery. I also know from personal experience removing a barbed hook from ones self is much more uncomfortable then removing a barbed hook.
Plus having barbless hooks aids in removing the hook from ropes, clothing nets ect. Perhaps I am the only one who does this but in a days fishing, some worse then others, I always manage to hook something else other then a fish!