Everybody is talking about it...
...so here's my two-cents:
For a cop, having a gun out isn't such a big deal. Pointing a gun at someone is a big deal. Waving it around would be a big deal (and would also show a lack of professional training). I understand others may see any display of a gun as a shocking development. But this is D.C. and this is a police officer. The streets are dangerous.
Simply having your gun out means there's a threat. Having your hand on your holster means there might be a threat. This officer has lived through a lot of threats and I don't begrudge him for feeling threatened by a large crowd. And from what I can tell he holstered up pretty quickly.
To me the question is why the guy got out his Hummer in the first place? That's the mistake. He could have just kept on driving.
[Though I should point out, because I haven't heard anyone else do so, that all the uniformed officers handled the scene very well.]
When you're in your vehicle, snowballs are not a threat to anything but your manhood. The only potential threat to the officer was created by the officer when he made a choice to exit his vehicle to initiate a useless confrontation with a large group of people. Christ, if you feel so threatened while driving your Hummer, what's the point of owning a Hummer in the first place!?