"I think you meant Blackball Tuesday.." the former San Francisco safety wrote. "I digress."

Reid is clearly still incensed over the way he believes the Niners treated him and Kaepernick in the wake of their police brutality kneeling protests in 2016 and 2017.

Reid and Kap have long claimed the 49ers punted them for starting the movement ... and also say S.F. colluded with other teams to keep the two players out of the league afterward.

So, when the Niners posted a blacked-out image Tuesday with the message, "Black Lives Matter #BlackoutTuesday" ... Reid didn't hold back.

"Hypocrisy:," the 28-year-old wrote, "the practice of claiming to have moral standards or beliefs to which one's own behavior does not conform; pretense."

Reid also went in on several other teams for their "#BlackoutTuesday" posts ... firing away at the Bears, Falcons, Cardinals and Texans.

Of course, all of this comes just a few days after Reid disagreed with former 49ers receiver Torrey Smith over the way 49ers CEO Jed York allegedly handled the kneeling controversy.

Smith claimed York "was willing to support in anyway possible" and also says York never told him NOT to kneel.

"He focused on helping," Smith said. "He has my respect forever."

But, Reid responded to Smith saying, "You speak based on your experience and I understand that. However, I can tell you that you never heard him say 'don’t kneel' because you never knelt. He begged me not to kneel."