Antonio Brown invited 6ix9ine to work out at his personal training facility in Florida ... and you know who's pissed off about it??
Pretty much the entire internet.
The Tampa Bay Buccaneers Super Bowl champ posted video with the controversial rapper on Friday ... running some 1-v-1s and easily catching passes over the rainbow-haired MC.
But, there's just one problem -- a lot of people have distanced themselves from Tekashi recently ... after the rapper was labeled a "snitch" for ratting out his gang member friends during his 2018 RICO case.