At this point, do you (anybody) really think it's possible to disarm America? The only thing you guys are suggesting is to disarm the good guys in the hopes of making it slightly more inconvenient on the bad guys.
As for the outcome the other night, I don't see much likelihood of the situation actually being worse. He took several minutes to shoot all those people. If nothing else, it would have been an improvement if he had to spend half of one of those minutes trying to defend himself. Also keep in mind, you wouldn't object if a cop, or even some rent-a-cop had gone in there and started shooting back, would you? It's a hard thing to quantify, but I'd put an educated citizen on the same level as your average cop in a panic situation like that. As is always the case, some people do better than others in a crisis, and being a cop doesn't necessarily make you one of the better ones. How many of those people you think had military training? Would you mind if they had been packing?
As for rubber bullets, what we've seen with asshole cops and their damn tazers is that if you give somebody a less lethal option, they're much more likely to use it. Contrary to SD's concerns, if you give everybody a real gun that actually destroys what it's fired at, nobody's going to run around shooting each other. You give them rubber bullets and you'll see people resorting to violence much quicker. It'd take less than a week before somebody got maimed over an otherwise benign road rage incident.
edit: it's also worth mentioning that there might well have been armed citizens in that theater who made the decision to flee rather than intervene. A responsible person will make that decision based on the totality of the circumstances. Not everybody who carries wants to automatically adopt the Paul Kersey approach. I wouldn't fault anybody in there if they decided that shooting back wasn't the best move under the circumstances.