In our group, there is a player whose decisions are more frequently called out as bad ideas compared to the others. Objectively speaking, by consensus with the GM and other players, these particular plans are usually not well thought out courses of action. As in not properly considering the presented scenario; that there are social cues being missed/ignored/misinterpreted, important details being totally forgotten/misunderstood/ignored, or trying time consuming actions to mitigate problems that the GM has said to not worry about. Certainly not all their ideas are bad. Its just that more often than others, their decisions are issues. As well, there tends to be louder reactions to these bad ideas than others' bad ideas.
Technically we'd be fine with making generally unwise decisions as long as it felt in character or at least interesting to the plot, but this feels more like an issue of occasionally just being entirely off base from the rest of the table. And he tends to get a bit defensive if we try to clarify these differences (or often, no attempt at clarification is made because in the moment, its unclear if he is just missing the detail).
The GM also occasionally injects some red herrings into the plot, and this player unfortunately has a tendency to latch onto and treat these as important. We've easily lost entire sessions due to pursuing these avenues of investigation.
By no means is he a bad player. He is a tremendously good sport about these decisions and how they work out, and he is quite helpful at the table for the more tactical/option side of the game. This often does work out to fun character interactions.
The issue is the degree of hostility from the group towards the player's decisions. What also doesn't help is that there have been times this player comes up with a potential course of action and it is quickly shot down as a bad idea, and then a little bit later, a different player proposes a remarkably similar course of action and its accepted by the party without question (there are key differences in nuance, but its not worth trying to justify or defend). He feels that people tend to just crap over his ideas because they are his. I would say this is not true, but just dismissing that statement is a self-fulfilling prophecy.
I will be frank, I am part of the problem here as well ("Why are you doing that", "I told you it wouldn't work", and to my shame plenty of other phrases I would prefer to not immortalize on the internet). I don't call him the player names or anything like that, but I certainly will say if I feel something is a bad idea. And if I advise a course of action that is ignored, I'm not above an "I told you so" if it doesn't work out well. I do not feel that my attitude is limited to this player, but it just unfortunately happens to be that he is the one with ideas I don't agree with. And certainly, I know I'm not earning any points in saying he occasionally makes "objectively" bad decisions (really its more for the sake of establishing the question; "the players decisions are bad, how does the group play nice?").
This ultimately came to a head in a recent game. The player in question initiated a series of actions that resulted in needing another player to take a set of time-costly actions (Pathfinder, using a total of 4 castings of teleport as a 12th level Wizard to transport 3 recently purchased/liberated slaves to a safe location). No attempt at asking for assistance was made in-character, instead he expended a non-trivial amount of personal gold to buy/free a couple of slave NPCs, and then with these freed slaves in tow, stated an expectation to the wizard solve the problem of getting them out of harms way ("I need you to teleport these 3 people to XYZ", no "please", no attempt to ask for permission or input).
The problem here is that the wizard player has a "My Guy Syndrome" streak about a mile wide. He opened with a resounded "Hell no!", and listed off a series of reasonably compelling arguments as to why his character would not offer the service (we're on a time crunch to literally save the world and doing this would easily cut two days off what is a race against time, he doesn't know these NPCs, these NPCs are not related to the current investigation/mission, his character is in a command structure and the asking player isn't his CO). I call this MGS in the sense that he is attempting to use "Its what My Guy would do" to defend the decision, no matter the harm it would cause the game, and the harm in this case is quite possibly the game ending on a whimper.
It also hit on a rather interesting side question of whether or not character resources (e.g. spellcasting services) should be considered party resources or not. The wizard player feels that once some detail is on their character sheet, and not on a table of party loot/resources, that control of that resource is solely the purview of the player; that you cannot demand/require that a PC expend some personal resource. It can be requested/freely offered, but contriving a situation that demands it is an issue. The problem essentially was that the wizard wasn't provided an out. The demand was issued and anything short of a "yeah sure" would be extremely problematic.
It is worth noting this freeing of slaves wasn't something the player did in a vacuum. The GM intentionally had these specific NPCs (whom the players encountered earlier) show up in this state, so the act of freeing them was intentionally an act of character building and with significance. It just wasn't relevant to the whole saving the world thing.
This, combined with a series of other recent events in the game (basically the same thing was asked of the wizard in a previous session and it was granted without question), resulted in the player becoming extremely upset. To the point of walking away from the table and basically ending the session 3 hours early (as he was the driver for another player). A couple attempts were made to talk it over, however all parties were far too emotional/proud to properly hash out differences. I suspect there may be some other significant personal issues going on for him (and understandably so, although it really is not for discussion here), however that does not excuse the treatment of the player by the group. I should note we're currently not even sure about the future of the game as a result of this. There is seemingly a very real chance the player might step away from the table permanently.
What are ways we can minimize hostility towards this player's decisions (and by extension, hostility towards the player) without compromising our views of common sense?
What are ways, in a roleplaying game context, to respect a person, but to frequently find yourself in disagreement with them?
How can we remain polite, friendly, supportive, caring, and edifying towards players who's decisions tend to grind against what the group might think as a good idea?