Justin Bieber Back Off Chris Brown!!! He's Like M.J. and 2Pac

Justin Bieber is defending Chris Brown in the face of backlash from other artists who don't want to work with him because of his history of violence toward women.

The Biebs buddied up to Breezy on social media Friday ... posting a picture equating CB to a mix of Michael Jackson and Tupac and saying Chris is being underappreciated like the music icons were before they died.

Justin says, "everyone wants to wait til people die To give them the credit they deserve. I'm calling it now when CB passes away after a long full life, you will miss what you had in front of you the whole time the people who have over looked this mans talent because of a mistake he made.. you need to reevaluate."

As you know ... Michael was dogged by accusations of child molestation before and after his death, and Tupac spent time in prison on sexual assault charges.

Brown pled guilty to felony assault of Rihanna way back in 2009, and he's also the subject of an ongoing lawsuit over an alleged rape in Paris.

As we've reported ... Scottish pop band Chvrches ripped Marshmello for working with Brown, calling it a tacit endorsement of violence towards women.

The lead singer for Chvrches, Lauren Mayberry, says the band's been getting death threats since speaking out against Brown.

But, Justin is firmly in CB's corner.

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