orcishgamer: I don't think the tank driver was ever willing to roll over tank man (please tell me if you're out of high school you know who tank man is, i.e. everyone, not specifically Darkk). A lot of people believe the US military (on the whole) would also refuse to harm US civilians and others believe that some of those "in charge" would like to change that.
It's more likely that we're simply continuing on our long quest to convert local law enforcement into something paramilitary in nature.
I don't think it's so much a matter of training the military to battle the US population; if it got to that point thing would already be well out of the government's control, and like you touched on it's likely a significant portion of the military would either refuse to engage the population, or may even side with the people (similar to what happened in Egypt). If there's anything more behind these drills other than just crappy timing then I'd consider it more along the lines of saber rattling directed at portions of the US population. Basically saying "We've been dealing with all you protestors using kid gloves. Keep in mind what kind of force we can actually bring to bear if you really push things."
EDIT: Just came across
this interesting bit of history. Seems the US army (tanks and all) were used against peaceful protestors during the Great Depression. I wonder if we'll end up seeing a repeat of history if the Occupy protests get significantly larger.
Primate: Perhaps you're right and the timing makes the whole thing a bit more sensitive. The needs of your armed forces are still there, though, and I'm guessing that these exercises reflect current training requirements.
That raises the question of just why the armed forces would suddenly need such an increased amount of training in urban combat, especially as we're supposedly trying to wind down the current overseas combat operations (unless, of course, we're now planning to invade Iran, which I wouldn't fully rule out). And even if one assumes that the military does need to conduct these kinds of exercises, there's the question of why the particular choice of location- conducting it in one of the largest population centers in the US seems designed to maximize its visibility, not minimize its impact and visibility to the population as one would think would be the more prudent course of action.