You missed david's point. You're not supposed to criticize the person (ex. "You are sloppy!"). You're supposed to criticize the person's work (ex. "Your work is sloppy!").

In my experience, criticizing the person just drags down their morale and usually doesn't motivate them, whereas criticizing their work sometimes motivates them to improve their work (it can also sometimes drag down morale as well, depending on how you go about it).

Depending on the organization, this is either acceptable or not, encouraged or not. And usually in every organization, if you're going to do the talking, you need to be one that everyone respects. Otherwise (again, depending on the organization), it can be a moment when everyone turns against you.

In especially toxic cultures, you need to be careful. It's unfortunate but true if you ever find yourself in one. Get out, get out fast if you are.

I think you are correct. Let me add two points: 1) Even though presenting constructive criticism may be uncomfortable for both parties, getting "blindsided" by the boss can really wreck a working relationship. 2) The reception one receives depends upon the prior relationship - a good one raises the probability of getting a "listening ear."