College hoops icon Dick Vitale is taking the NCAA to task ... blasting the league for having a dirty underbelly and calling for the jobs of any coaches found guilty of corruption.

"There’s a cesspool that’s existing in college basketball and on the scholastic level," Vitale said -- taking aim at NCAA eligibility requirements and AAU basketball.

Dicky V says he's "crushed" over the FBI corruption sting that came to light this week ... where 4 CBB coaches were arrested and charged with federal crimes. 

The legendary analyst tells us to reserve judgement until the coaches have their day in court ... but stresses that these allegations cannot be taken lightly now that the feds are involved. 

And if they are guilty ... Dicky V knows what has to happen -- "THEY MUST BE FIRED."