Sadly, it's almost everyone ... even lots of those who tend to put their "let them go" mask on whenever they need to. Fact is, I know of only three Forks resident guides that do not kill. Some kill most of what they can, so they can get their "limit" and be done early ... others let a near-majority go, and a few kill just a handful. To me, it boils down to a mater of integrity and is black-and-white: you either do or you don't, and few don't. We know their plight throughout most of their range, we know that harvest is a contributing factor, we know that these fish are being hit harder than ever, even if being let go in response to being the only fishery left in the state ... but only a couple are willing to live by their belief of lessening their impact before the almighty dollar.
Those that kill a a lot often justify it by saying (these are actual reasons given that have made it back my way): They're all going to die anyways or There's so many that they are spawning on top of one another.
Others know that they probably should and always say: well we've only killed a few, or It was there very first one.
Sadly a number of peeps that post here mention folks suggest that the guides they use / businesses they frequent practice or support WSR all the time, guess what, virtually none of them do so.
Yes, it is legal and why I rarely ever make a fuss on the water, but I will gladly state my opinions here and elsewhere in the appropriate setting. We've lost 99% of the steelhead rivers in this state now ... for a variety of reasons, but all under WDFW management. We have a handful of rivers left hangin' by a thread to runs that often haven't met escapement in the last 20 years, such as the Hoh ... so even though the visionaries say it's okay to do so, I'm going to make that safe bet and say that these fish need a little more protection that the state says they do.
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Seen ... on a drive to Stam's house:

"You CANNOT fix stupid!"