LeBron James -- Alleged Mishegas at Jewish Basketball Game

LeBron James was the target of some Old Testament aggression after a Jewish league basketball game this week ... when a man in the gym UNLOADED on the NBA star over an alleged anti-Semetic comment.

As we previously reported, LBJ was a last minute fill-in for a team at the Mandel Jewish Community Center in Ohio Monday night ... and his team, CRUSHED their opponents.

But after the game, LBJ was verbally accosted by a man who worked at the kosher sandwich shop inside the center -- who claims he heard LeBron telling his buddies, "These Jews suck at basketball."

The man tells TMZ ... he definitely fired off some choice words to King James -- including, "Princess James Get out of Cleveland" and "F**k you, you ruined the NBA."

The man says he was later contacted by his boss, who suspended him from his job for 3 days over the verbal attack.

A rep for James tells TMZ LeBron did not make the comment in question.

TMZ received a statement from a Jewish member of the team LeBron was playing with that night -- who tells us the allegation is "nonsense" ... and insists LeBron couldn't have been nicer to everyone at the JCC, both Jews and non-Jews.

For the record, LeBron has a pretty good relationship with the Jews -- besides dabbling the in the Hebrew basketball league ... he's also tight with a pretty famous orthodox rabbi.