It is irresponsible, but I think you're overstating the risk. This looks like footage from a gopro (due to the wide angle shots). This only requires a small drone to carry, like the DJI Phantom. The total weight for the phantom and camera is going to be something like 2.5 lb, and that weight is spread across a device that is rather large.

I wouldn't want to get hit on the head by one, of course, but I don't think it would be possible to kill someone since its terminal velocity is going to be pretty slow.

No, you are wrong. From that altitude it can do anything from severely disfigure, paralyze or, yes, kill someone. Did you see that shot where it flies right by that crane? Irresponsible doesn't quite describe it.

I've been deeply involved in RC flight for over 30 years. I cannot imagine how these people think it OK to fly toy-grade products over people like that. A DJI with a Gopro is a toy. I have $10,000 RC helicopters and planes. They are fucking toys. Having seen the range of failure modes I have over the years I can only characterize these people as irresponsible morons. I also say this from the context of having designed and manufactured high quality electronic products for the RC and military targetting drone industries.

I'm just waiting for someone to create a (fail-safe) parachute for those devices so we can just move on from the "it's gonna fall!" arguments.

It doesn't have to be about the weight/speed. Unless it actually crashes in a fail-safe way, it may keep the blades spinning. It's very unlikely to kill you, but can easily cause pretty deep cuts.

I play with rc planes usually and would really like to see some docs on failure modes / failure rates of typical *copter drones. My planes / controller failed enough times that I'll probably never fly any toy over people. Maybe the newer models are much better. I'd like to know if that's the case.

Maybe I'm crazy, but in my judgement, the risk of occurrence for the ultra-bad (somebody dies) is low enough that its outweighed by the good (the world gets to see dramatic and illustrative views of how big a protest this is). Even the minor-bad (somebody gets cut or bruised) is still pretty low occurrence risk (its so slow and low that the crowd see, and is waving at the drone)

We used to be chased by wild cats, twice our weight, in tall grass, and now we limit use of anything that might even scratch someone else. Society's great and all, it provides a good support net and enables a lot, but its trend towards conservatism is frustrating sometimes.