When we ride in the park, we're typically two across, but to be honest, where there are two lanes in each direction, we'll take the whole lane. In that situation, I feel it's safer for the cars to move to the outside (same direction) lane to pass us, than for them to try to move over slightly and pass us with another car next to them. (Car in outer lane, car sharing inner lane with us.) The traffic is typically very light, especially later in the day. It's a closed loop - there is no through traffic, and all cars have to pay to enter the park - bicycles and peds are free.
The group in question probably was going too fast. But just like a pedestrian shouldn't step out into a line of fast-moving cars, the policeman shouldn't have done the same. Yes, an animal could have done the same, and there wouldn't be an issue - that's an accident. This was intentional.
For 3 days, I get to part of a thousand other journeys.