The rainbow-haired rapper broke his silence Friday with a social media post saying, "what happen here was nothing but cowardly."

Tekashi says he's not mad about being jumped at an LA Fitness in South Florida, explaining ... "In the street there's no rules so I can't say they were wrong." Still, he says it wasn't a fair fight.

6ix9ine took some more shots at the three men arrested over the attack -- Rafael Medina Jr., Octavious Medina and Anthony Maldonado -- saying ... "Just imagine having nothing to do with a situation and feel obligated to make it your business. (Very weird)."

Tekashi also claims he's been walking around without security for the last two years and says people see him out in public all the time. He says, "I really never hid from anything."

The beatdown sent Tekashi to the hospital but he says he's "happy to be here still."

In his P.S. he takes a parting shot at his attackers -- one of whom law enforcement says is a known gang member -- saying ... "I never knew we respected jumping people. When did that ever become a W???"