Radical honesty is considered abuse, especially when your observations are 100% empirically true and spot-on and everyone can see it including the person targeted.
They wrote about this problem 3000 years ago. "Correct a fool and he will hate you, correct a wise man and he will love you".
I think you have come up with a great criteria for deciding when to be honest.
As someone who has lived a very honest life I can say with confidence, it doesn't work. It's made my life less happy, not more. I still do it out of habit, and also for the feeling of moral superiority I get, but if anything I am thinking about being less honest rather than more so. It just creates too many problems, especially if you are an entrepreneur or business person.
They wrote about this problem 3000 years ago. "Correct a fool and he will hate you, correct a wise man and he will love you".