John, I don’t think it’s off-base to avoid talking to police officers. As individuals, they may be very nice people but they themselves are not free to interpret orders from above. When it comes time to act as a group they will do what they are told — they have no choice. The dynamics of a protest can radically change people’s behaviors and how you might approach a single beat cop walking down the street is very different than a large group of police assigned with keeping order.
Not that I expect this to be taken seriously by anyone:-) Until the situation arises, it’s always preferable to be polite.