I'm definitely wary of the concept of dismissing courtesy when working with AI agents, because I certainly don't want to lose that habit when I turn around and have to interact with humans again.
There's a very large gap between being super nice to a human and being a jerk.
I don't think it benefits me much by very politely suggesting that its approach may not work and emphasize on the good part of the idea it generates and it would be better if it could try to push in another direction for example X. Like I do when talking to junior engineers.
I usually just say, "This does not work because of ..., Y is good though, change your mind and assess X now". I can also say this when I'm not actually sure whether X works or not, without worrying about my words sending an intern / a junior engineer into days of struggling on a deadend.
