Asking about his legal rights was perfectly reasonable especially since he was not breaking any laws. His behavior was always polite, the officers knew he was not breaking any laws and that he did not have to answer any questions. They tried to provoke a response from Bierfeldt, failed, treated him in an abusive manner, and got caught. Blaming the victim, Bierfeldt, for how he was treated is distracting from the issue at hand.

That issue is, Was Bierfeldt legally required to answer their questions? since the answer appears to be no his behavior is inconsequential.