C&R is fine. Catching to eat is fine. I cannot say how or why others do what they do. Or even guess as to their motives. That is up to them.
I fish a lot. For the past twenty years, trout only. I keep smaller fish in the 8-12" range. I release larger fish, unless they are damaged. I have caught fish with hooks in their throats, hooks in their gills, missing an eyeball, scars on their backs, and all sorts of deformed and damaged fish. In the waters of the ADK's, mostly, bacterial infections, et al is fairly mild. Most places you can drink the water if you are willing to risk gardia. Worms, cycsts, etc IS a real problem through out the area. If you keep a fish for eating, make sure he is well cooked.
I may catch 15-20 trout before heading back to camp. I do not gloat, nor do I proclaim trophy if I happen to catch a good sized fish. He goes back, usually. I have landed 30" rainbows (so called steelhead) on 3# test with a size 20 blue winged olive. It is not a big deal to catch a 15" brookie on 2# test line with a size 16 coachman. It is a big deal when one of these fish is full of eggs, though.
Mostly, I don't carry a rod out hiking. When I do, it is because I am looking to extend my food in the woods. 5# of trout will last two days of good eating. I make no bones about it, I hunt fish to kill and eat. If I don't catch anything, I eat plain rice or macaroni. I also enjoy fishing. It has a survivalist feel that makes me remember where I came from. Where we all came from. Nor am I needlessly cruel. If, I decide to keep a fish, I break his neck before I remove the hook. That quick. Releasing is MUCH more difficult, but it helps a lot to turn him upside down. You get about 10-15 seconds of disorientation to remove the hook and set him back in the water. My hands are always wet from picking him up with the net anyway (if he fits.) With flies, 95% of the catches are in the jaw or lip. A barbless hook means it will slip out easily. With midges (size 20,22 and 24), it is ALWAYS in the lip.
No, I never feel that I am chasing the fish to inflict fear and pain upon him. I am hunting the fish to kill him, he knows it. He may or may not survive. I figure that a 2# tippet and size 20 hook makes it about even. If I catch him, and I am hungry, he is prey. He knows that. He kills minnows to live. They are prey. He kills insects to live. They are prey. I may kill him to live out on a long hike. There is no question of catch and release. If I am not hungry, I would not fish. So, the question is rather incomprehensible. But, in a more civilized manner, I release larger fish, knowing that they will reproduce far more effectively than the 10" fish I just killed. This insures tomorrows "survival".
Do all the fish I release survivve? Well, I doubt it. But, I am sure that some do. A better proportion than none. So, I sort of agree with both sides. Some simply die from exhaustion. Some simply die for no apparent reason...too frighted to eat? Some survive. Enough, I think...