Or another possibility that occurs to me ... he pretended not to see the alleged spitter, because if he and the cop confronted the guy, and the guy told his side of the story and turned to ask for corroboration from others standing around him (protesters, female cop), the whole incident would have been documented in the black cop's report as a misunderstanding of Cleavers.
By pretending to be unable to find the "perp," he can make up any story he wants about the guy and who's to know? (Except for that damned videographer filming the whole incident! Ha!)