That's quite a mixture of metaphors, @Stevie_brute. Touche'
Where is IM Pfren???

To be fair, you can fully disclose that an idea is wrong yet deliver it in a gentle way. If I think a move doesn't make sense, I'll just tell them I don't think x move is useful because any threats it makes can be easily met, then maybe giving some example variations and tell them to keep that in mind for next time. But there are more aggressive ways to say that, such as "why on earth would you put your rook here when it does absolutely nothing?" I'm sure it's not because that person was too dumb to know that doing absolutely nothing is bad, but simply isn't good enough at chess to know how useful or not his move was. This tone does of course bring attention to a fault in the person's play, a useful thing, but it's not the only way it can be done.

The "kinder, gentler" approach doesn't work with all students.
Many students respond better to a kick in the pants.

I think if a student really does want to know his problems, and is willing to work hard to improve, then simply having these problems brought to his attention in a plain and clear way will motivate him to improve in those aspects, and I don't think this requires particular aggression. If the student knows what caused his painful, frustrating loss, he should be pretty motivated to eradicate it. This is of course in addition to any exercises the coach wishes to give.
There is a big distinction between delivering the truth in a reasonably gentle way and engaging in "white lie kindness," where you say things like "This move isn't too bad even though you go from winning to having mate in 3 coming" -- this does not deliver the truth. White lies are in fact a big pet peeve of mine. The truth does not alter itself to make people feel better, but it doesn't yell at people either; it just firmly, yet with no hostility, delivers its message, nothing more.

I'm with <Elubas> on this one.
Personally though, I never saw anything from Pfren which really bothered me in this sense.
Also, as a coach, sometimes it's just too hard to refrain from venting your aggressions just a tiny bit... but how and how much is greatly a question of taste, I guess...

Takes a long time to shave a beard like that.
Don't make fun of my friend.
Anyway, he's back!

a fair amount of tripe here. IM Phren wandered over to posts I had made, gave ansolutely accurate critiques, and, I dunno...maybe a joke, too, but, his small alaysis was very helpful to me.
I find that whiners really don't put much value in being called "wrong" and that seems to be the way of the world. He had the patience of a fisherman! I remember a guy here that went by the name of Veraslov...(yeah, close, but no cigar) and veraslov was adamant about having invented an opening.
Imagine the coincidence, eh.... The opening he claimed to have invented was the Veresov.
Phren pleaded with him, gave near endless examples of how old the opening was, wrote about Veresov himself, and yet, day after day, the Vereslov (or whatever name the guy used) would come back with weak answers about how it was his, he had never seen any games by Veresov, and went on and on about how great he was.
Not accepting challenges, mind you. Just saying he was really REALLY good. I have no idea how IM Phren reached deep in himself to face this strangest of all whack jobs ever. But he did. I followed for a while because some comments started splintering off into new topics, and some were great learning tools. Thank you IM Phren, for showing such patience, that just that it was nothing short of a class act.
If he's gone, then leave him have a break. You ever take a vacation and have your boss call you halfway through the time and ask you to come back? What would you say? well...strike that. Some WOULD go back. I would. I'm a worker, for crying out loud.
But dang, let him get a breath of fresh air, taste the companionship of friendship and laughter, and maybe if he's lucky a fine wine (Icewien is good this year) or even a shot of good whiskey...Crown Royal, say. Or, bourbon...Jim Beam. Maybe tea!
The point is, some folks take a break, they need a break, don't feather them up when they are on a break.
Please.
Don't think of them as gone....
Think of it as more of a longer holiday than the weekend was willing to relinquish...
One more small thing. ALWAYS remember, that in case of fire...

To be fair, you can fully disclose that an idea is wrong yet deliver it in a gentle way. If I think a move doesn't make sense, I'll just tell them I don't think x move is useful because any threats it makes can be easily met, then maybe giving some example variations and tell them to keep that in mind for next time. But there are more aggressive ways to say that, such as "why on earth would you put your rook here when it does absolutely nothing?" I'm sure it's not because that person was too dumb to know that doing absolutely nothing is bad, but simply isn't good enough at chess to know how useful or not his move was. This tone does of course bring attention to a fault in the person's play, a useful thing, but it's not the only way it can be done.
I once was lucky enough to take some lessons from an IM in a group for a few days. His comments towards me were like "but don't be a thick!", "ok, for the material, as every patzer does", or "that combo is more fake than Judas!" I really miss the guy.

Here's what I think personal lessons from IM pfren might be like (worth watching, I promise)
https://www.youtube.com/watch?v=VnuImW1dWAk
I doubt very much he'll be back to hear deluded sub-experts tell him how wrong his analysis is. The deluded sub-experts may now continue rolling in their own feces, free from accurate criticism ... which is no doubt what they wanted. Big pond, but no smart fish.