A photographer was mildly assaulted for taking pictures of PINK changing her daughter Willow's diaper.  And it was caught on video.  (FYI:  Willow turned 2 this month.)

This went down Wednesday night at the Malibu Country Mart.  After the guy got a little too intrusive with his camera, Pink's husband CAREY HART and a friend of his confronted him.

Carey's friend stomped on the photographer's foot, then kicked his camera to the ground.  He didn't pull out some Bruce Lee-type move and kick it out of the photographer's hand.  It was on a table.

Police and paramedics were called to the scene.  The photographer claimed Carey's friend also kneed him in the groin. 

But apparently, witnesses didn't back up that claim, and the cops weren't impressed with his side of the story . . . because they didn't do anything about it.

The photographer obviously wasn't happy about that, because he yelled at Carey and his friend as they left in an SUV.

He said, quote, "Carey's a punk-ass [B-word]."  This guy in the white assaulted me . . . [he] kneed me in the [groin] and the sheriffs didn't do nothing . . . because celebrities get special treatment in Malibu!"

(Here's video.  WARNING!!!  The photographer drops several B-WORDS.)

(You don't see the incident that caused this chaos, and Pink is barely in the video.  There's just a quick moment where you see her from behind, leaving the scene with Willow.)

(There's also no knee to the groin, but that doesn't mean it didn't happen.  It may have occurred before the video started.)