Kevin Hart, Cedric The Entertainer, Michael Blackson Respond to Katt Williams

Katt Williams predicted his "Club Shay Shay" interview would have the internet in shambles ... and now some of the guys he attacked are fighting back.

Kevin Hart called Katt's comments "sad" Thursday but didn't squander the opportunity to plug his new action movie "Lift" with all the unsolicited buzz from the interview.

Katt essentially labeled Kevin the "Jussie Smollett of comedy" -- a charlatan who was planted in the movie industry after arriving in Los Angeles from Philly without any real buzz, and claims to have turned down plenty of lowbrow roles that Kevin happily scooped up.

Kevin and Katt have been at odds for years -- Kevin claimed Katt flamed out on drugs during a 2015 Breakfast Club interview, to which Katt recently told Shannon Sharpe he's never done a hard drug in his life.

Not to be outdone, Michael Blackson didn't let Katt slide for accusing him of using a fake African accent throughout his career ... but still gave him his props at the end of the day.

According to Mike, Katt ranks as the #4th best comedian alive (he ranked himself at #10) but thinks his 2005 glory years are long behind him, Mike claims he saw Katt get heckled in his Cincinnati hometown before ... a terrible look for a legend.

Cedric The Entertainer also got pissed over Katt's continued allegations he was a joke thief but hinted that he wouldn't be participating in the back-and-forth mud-slinging.