There's no excuse for rudeness so I would complain.

That being said one of AA's regional carriers, I think PSA, does have it written into it's procedures that rollaboards must be gate checked even if they fit, and as it's in their manual, it then becomes enforceable like other FAA rules. Again though that doesn't excuse rudeness and instead could be explained better so people aren't confused when their bag which fits fine on a CR7 operated by anyone else isn't allowed.