I am one of those "extra" honest people. It's a fine line to walk on, and very hard to not be an asshole about it. In my opinion, it requires big level of empathy, that most people are born without.

First, one needs to ask themselves if they would be OK with the same thing being said to them. Then they need to ask themselves if there's any benefit to the other person/group/business of you saying that. And finally, how to say it without being offensive. But, it also takes a lot of balls to pull it off, because it only works if you do it 100% of the time, even when it's you that's on the line.

Example Boss: who did that huge mistake? You, mid-level manager: It doesn't matter. Ultimately, I'm responsible for that person, so it's my fault. If you want, I will start packing immediately.

See, blaming John can also be regarded as being brutally honest in this situation. I mean, it's his fuck up; without him, you wouldn't be in this situation after all. But that's not 100% honesty, is it.

Now you lost your job. You need to pack your things. John asks what happened. What do you tell John? I mean, you're brutally honest, after all. If you say nothing, John will never learn, might make the same mistake in the future, and it will be two lost jobs in the end.

Think and answer for yourself. See if you pass the "Am I brutally honest person or just an a-hole" test. If you do anything else than

nothing. Not your job anymore. Saying anything will just make John feel bad, and you gain nothing. Company might, but why would you care now

you're just an asshole. Probably with god complex, too