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KATT WILLIAMS SAYS HE SMACKED TARGET EMPLOYEE FOR CALLING HIM A NI**A!

Katt Williams claims the reason he pimp-slapped a Target employee in the face last month is because the guy called him the n-word ... and TMZ has video of Katt's explanation.

Katt was performing last night at the Comedy Store in Hollywood when he described what went down immediately before the November 25th attack in Sacramento -- telling the audience, "This is what the dude at Target said ... 'Your assistant is already suing you, you p**sy ass n***er."

The jab is a reference to this lawsuit -- in which Katt's former assistant is suing him for $5 million, claiming the comic punched her.

Katt said he flipped when he heard the slur and asked the employee, "Did you just say the n-word in front of Katt Williams?" -- to which the employee answered, "You say it all the time."

Katt says he shot back, "Say it again and see what happens" -- and that's when he knocked the guy upside the head.

Katt then compared his racism plight to that of Dave Chappelle, explaining, "That's the same sh*t that drove [Chappelle] out of the f***ing business."

Katt seems to be alluding to Chappelle's claim that he quit his Comedy Central show and went into seclusion over an argument with producers about a sketch that he believed was racist.

The Target employee -- a guy named Forrest Liebenberg -- was fired from his job shortly after the incident. Target wouldn't explain why. Multiple calls to Liebenberg weren't returned.