Assuming that the police were actually required to protect and serve then their oath demands that they protect the speech occurring at the parade, no matter how repugnant they find it. The first amendment protects all speech no matter how offensive it may be.
They cannot, however, be required to participate in an event, such as the police in Tulsa being forced to attend the Muslim event. Also, calling someone who disagrees with you a bigot is bigoted in itself.
They cannot, however, be required to participate in an event, such as the police in Tulsa being forced to attend the Muslim event. Also, calling someone who disagrees with you a bigot is bigoted in itself.