Cardi B was NOT the drama on the opening night of her new tour ... but her fans were!

Cardi B warned ICE agents she'd fight them if they showed up at her Palm Desert concert, drawing massive cheers from her Latino fans.

Cardi B was NOT the drama on the opening night of her new tour ... but her fans were! A parking lot brawl broke out after the show, which ended with an innocent bystander's car getting a hot dog ...