Tekashi 6ix9ine has been hearing an earful from his fellow MCs about his snitching -- it's been all bad -- but T69 has a theory on all that ... they're jealous and running scared.
Sources close to the embattled rapper tell TMZ ... Tekashi is well aware of the hate he's been receiving either on camera, in interviews or on social media from his peers, but he doesn't give a crap about any of it -- 'cause he thinks those folks are foolhardy haters.
In fact, we're told Tekashi has strong words for those people -- which is a LONG list at this point, BTW -- and it goes something like this ... just wait and see.
According to our sources, Tekashi believes him testifying against his old crew will be forgotten almost instantly as soon as he's released from prison -- and he also thinks he'll be more popular than ever with the masses ... which, of course, means $$$$ in his pocket.
We're told he thinks that anyone in the rap game who's spoken ill of him since this whole legal ordeal began are not only envious, but threatened by him ... afraid that he'll pass 'em up and leave 'em in the dust when he gets out and starts making hits again.