There's only one word that I used when I am at this same position. It's called moderation. You have to get your message out, no one pays you for being a nice guy but then you have to pass it along with moderation less you miss the point and create avoidable enemies.
If you are blunt to someone and the person hates you for that, I think the person just wants to hate you.
I have come across people that i was blunt and direct to and they hated me in an instant and I reciprocated the same gesture as quick as possible.
How dare they dislike me for speaking the truth.