So it didn't happen in the first place - but if it did, it was only reasonable behaviour on the part of the authorities?

The Denver Post has a story about the chaos caused in Denver by police precautions - no mention of this incident as such but "thousands were caught in the frustrating morning slowdown that included at least one minor accident." That sounds like it could well be tactful reporting of this one.

Anyway, whether it happened or not, it's OK for the police to do this kind of thing then?

I assume that the Moscow police in the old days would have had the same kind of explanation for confiscating cameras and rouging up the imprudent photographers, and so forth - after all there have always been plenty of people who didn't like the Soviet government that much. But I always had the impression that the democratic West didn't buy those kind of explanations. But clearly it's a completely different situation now.