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The acetyl group (-COCH₃) is not acidic itself. The amino acid has both an acidic -COOH group and a basic primary amine (-NH₂) group, but in the compound the primary amine becomes a secondary amine (-NH-), who basicity will depend on surrounding atoms. (If you look at a structural diagram of the compound, the only hydrogen atom it can realistically lose to have acidity is on the -COOH.)
Maybe the one guy was just telling the story of how he overheard someone with a ping pong paddle saying RAGARAGARAGARAGARAGARAGA