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Kanye West just attacked an 18-year-old guy inside the waiting room of a chiropractor's office ... TMZ has learned.

Kanye and Kim were in Beverly Hills when they were swarmed by photogs. We're told the 18-year-old came to Kim's rescue and held the door of a medical building open so she could get in. As Kim walked, the guy allegedly said, "F**k these fa**ot-ass n****rs"" -- referring to the paparazzi. Kim then told her it was not appropriate to use the N word. We're told he then screamed at her, "F**k you bitch. Just trying to help you. Shut up n****r lover, stupid slut."

Apparently that got Kim hot as fish grease ... she watched the guy walked into an office. A short time later Kanye arrived and went into the office.

Sources say Kanye and Kim rushed into the waiting room of chiropractor Richard Hill and found the 18-year-old sitting there. Witnesses say Kanye punched the guy and Kim screamed, "We have it all on tape."

Sources say the massage therapist in the office separated the 2 men. Beverly Hills cops were called and the 18-year-old said he wanted to press charges.

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