Do you think the Police play favorites at protests and demonstrations?

Yes, as long as cops are human, their mental default setting will most likely be to protect the status quo (who signs their paychecks?). If you have video proof of this incident, try contacting the CHP Internal Affairs office, or perhaps the state Attorney General. I can't guarantee their response, but if nothing else there would be a record of the problem in the event that you need to pursue this matter in court.