Joe is a former Marine, and a cop. His position on the SWAT team requires him to tell it exactly how he sees it. Joe cannot help but to be perfectly blunt and frank.
Some might find it offensive, calling him tactless, or maybe even inconsiderate. That's not the case at all. He's simply an honest man. He does not lie. He can't lie - because of his strength of character, and his job. He is honest. He pulls no punches. He calls it exactly how he sees it.
For people like Claudette and Pete, Joe's frankness is an endearing trait. They love his honesty. They know his heart is always in the right place. They know they will never find another person more loyal or more honest than he.
Michael, however, does not appreciate Joe's bluntness. Joe doesn't hold back, Michael wishes he would. Michael is too sensitive and insecure to fully accept Joe's frank speech. Joe's honesty also means that Michael doesn't always hear what he wants to hear. That is something that Michael doesn't handle well. Not at all.
Whatever your opinion on frankness, it is a very strong trait of Joe's. Good, bad, or indifferent, that's just who he is. Frankness is just one of Joe's many strong qualities.