John Salley says the Ja Morant critics need to pipe down ... telling TMZ Sports he truly believes the NBA superstar didn't have bad intentions when he appeared to do a gun celebration on Tuesday night.
Salley told us the firearm-themed gestures -- which Morant seemed to hit following a thunderous alley-oop dunk in the Grizzlies' overtime win over the Pelicans -- were merely "a part of hip hop culture" ... and nothing more than that.
"He's not saying, 'Forget ya'll -- I got my gun!