Lots of if, would, should have, could have, here. Also, lots of things we don't know such as:
-Did the cyclists see the 2 cops at all?
-Did they see the cop making a sign to pull over? When he made the sign with his hands, both cyclists were already engaged in the intersection. I don't see the cyclists looking at him in the video nor hear him yelling at them to stop.
I don't know for you, but I am always looking to where I am heading when I ride (or drive my car), not somewhere else
-Did they ignore the cop telling them to pull over on purpose?
-Was the high speed chase with sirens & lights flashing necessary or was it an adrenaline driven power-trip?
-Was the arrest necessary? IMO, a simple warning or a fine for failing to stop at a stop sign would have sufficed...
In their line of work, police officers must make judgment calls pretty quickly, sometimes on the spot. Since there was no health or safety risks, I believe that cop lacked judgment by making this call and putting a cyclist under arrest (without telling him his rights & stating the reason of his arrest). He was most likely in an adrenaline rush. Emotions can override rationality.