The golden rule prevents me from padding my criticism with a layer of poetic fluff. I (and I assume others) readily see through obligatory rhetorical nonsense. I find it irritating and insulting, because it implies that you think you're tricking me into thinking that I'm not receiving criticism, and that I would have irrationally overreacted to your criticism if you hadn't cunningly veiled it.
If we are working together, I want your honesty, and I do not want us to fail together because I've done something wrong and you were too "polite" to express your genuine disapproval. If I'm dealing with a child, or someone who is very emotional and not very smart, perhaps, I should adopt your patronizing scheme. But I will not treat my technical coworkers like children, and I expect the same of them.