The Louisiana rapper recently sat for an interview with VladTV, in which Kelly's conviction was brought up ... and Boosie was asked about it. He didn't hesitate to let everyone know how he felt about the case -- and that feeling is ... bitter resentment.

Check it out ... Boosie says Kelly got railroaded on similar charges he was facing in 2008, and thinks much of that has to do with his race.

But, then Boosie took it a step further ... justifying Kelly's actions as it pertains to his victims, brushing it off by saying, "I just feel like R. Kelly like the young bitches." There's more ... Boosie goes on to say claims R. Kelly kept his victims under his thumb at all times is BS.

He adds, "If you leave a bitch at the house, and you go on tour for two weeks and she don't go nowhere -- that bitch ain't been kidnapped. She waiting on daddy to come home."

Boosie also claims a "bitch ain't been sexualized if she been in the bed with three, four women. You know, she hasn't been (taken) advantage of, because ... she is willing!" He ends by saying Kelly's only mistake was the "age part."

The host, DJ Vlad, finally stepped in and pushed back on Boosie's wild characterization ... pointing out that Kelly was dating -- and eventually married -- a very underage Aaliyah way back in the day ... and not just that, but had gone to court over this exact issue over a decade ago.