The phrase "blunt message" means conveying a direct and straightforward message without using any soft or subtle words. It is often a straightforward and clear explanation without any sugar-coating or beating around the bush. Full definition
Bayern Munich president Uli Hoeness has sent a pretty blunt message to rivals Borussia Dortmund after they let Pierre - Emerick Aubameyang leave the club for Arsenal this January. (caughtoffside.com)
It's hard to see how else they could have acted, but it's necessarily blunted their message. (politics.co.uk)
Just as you put taxes completely off your mind until next year, you get an unwelcome letter in the mail from the IRS with a very blunt message: Your tax return's been rejected. (policygenius.com)