Charles Barkley -- Barack Obama Bracket Haters ... You're Just Racist!

Charlie Sheen -- and anyone else who's mad at President Obama for filling out an NCAA tournament bracket -- is really just an old fashioned racist ... so says Charles Barkley.

Sr. Chuck and his "Inside the NBA" co-star Kenny Smith were leaving the London Hotel in NYC when the two went off on Obama's bracket critics.

"What, is he not supposed to think about anything else?" Smith said.

Barkley was more direct -- "Listen, you people in America who are upset that President Obama did a bracket ... why don't ya'll just go say you don't like him because he's black."

He continued, "Cut through all the BS ... don't say he take too many vacations ... just say, 'We don't like him because he's black.'"