According to new legal docs obtained by TMZ ... Isaiah Lee -- who makes a point of saying he identifies as bisexual and has experienced homelessness in his filing -- says he rushed the stage to tackle Dave as a protest against jokes he made during the evening.

Lee says the venue's security team brutally beat him after he tackled Chappelle, allegedly spitting on him and dislocating his elbow purposefully ... and, he claims, the team allowed Chappelle's entourage to whoop on him as well.

BTW ... Lee says the knife that looked like a gun fell out of his pocket during the beating, and he never pulled it out to use on Dave.

The plaintiff also claims the venue knew about Dave's propensity for telling offensive jokes, and should've taken action to prevent potential harm caused by said jokes -- presumably, including ones about transgender people ... for which DC was famous by then.

Lee's suing for negligent security and battery ... claiming he's suffering from back injuries, loss of mobility and the aforementioned dislocated elbow -- as well as other medical issues. Worth noting ... Dave himself is NOT a defendant here -- Isaiah's just going after the Bowl.

Remember ... Lee took a plea deal in the Chappelle case -- pleading no contest to a pair of misdemeanors ... entering a restricted area during a live event and battery. He was sentenced to 270 days in jail.

BTW ... Lee's maintained his claim he attacked Chappelle because his material triggered him -- first making the statement shortly after the incident in 2022.