I think I should tell people the truth even if it's not what they want to hear. What say you?
That depends. Do they not want to hear the truth, or do they not want you to keep haranguing them all the time?
I make people angry because they don't want to hear what I have to say to them.
You know it is right to tell people the truth. If someone asks you to not say anything about it then you should respect their wishes. They will get so angry about it that they might punch you unless they have patience of a Saint.
It's on them if they get violent. I'll call the cops.
Yes, it would be wrong of them to react violently, but that doesn't mean you should harass people with your truth if they don't want to hear it. In the end you just need to pick your battles. You'll probably find people more receptive if you do.