Unless a one-hook rig is fishing hangback, it's capable of mortally wounding fish just as easily (if not moreso) than the dreaded 2 hook rig you are demonizing.

How a guy rigs his gear makes a HUGE difference.

Understand this.... the fish is trying to engulf/ingest whatever it is you are offering up... lure or bait.

If the hook is attached directly to or buried into the offering, that hook will be ingested right along with the bait/lure of choice. I don't give a flying [Bleeeeep!] if it's a fly, a jig, a spinner, a spoon, a plug, or a baitfish... there is significant risk that the hook could mortally wound that fish.

The best way to avoid a mortal hooking wound is to ensure the hook NEVER enters the fish's mouth. Either don't fish, or rig that hook hangback.