I just don't see the "bully"-like behavior on his part here. She was given a legal order, she ignored his advice and gave him lip besides, and she paid the price.
She was done with her phone call and walking when he approached her and said she had been talking too loud. Can you imagine ending your phone conversation and a cop starting with you by saying that you talked too loud? Tell me you wouldn't be tempted to say, "What?!?!?"
Orders? wtf, is this a military State now? You get arrested for talking too loud on your cell phone? Sometimes I call my elderly, infirm mother on my cell phone to check her and I have to practically shout because she's nearly deaf. This thing smells.
I think the people who back the cop on this one would take the complete opposite side if it happened to them. She could have been ticketed and fined perhaps, that would have been more than enough for the "crime".