Agreed....nether did the Oklahoma bombing.
In other words a madman with an intent to generate a high death toll will attempt to find a method and means to accomplish their murderous tasks out of sheer determination and lunatic style meticulous planning. Pretending that banning all guns or enforcing draconian gun laws and/or self-defense laws will somehow protect us from these types of people is well beyond reason and logic.
Whatever you think about gun control laws, your logic is overly simplistic. No approach can completely solve a particular problem, but that doesn't mean we're not better off using that approach anyways. Seat belts, airbags, anti-lock breaks, better vehicle standards, etc, don't totally prevent driving deaths or injuries...but that doesn't mean they don't help.
Would a madman be able to kill a crowd of people at a movie theater without assault weapons or guns in general? Maybe, but the whole point of a gun, and the reason people argue so strongly for widespread gun ownership, is that it's a LOT easier to kill people with a gun than pretty much anything else. Of course that can be used for good, which is the point of pro-gun arguments, but it clearly can help bad guys as well.
I'm not necessarily against gun ownership, I just think it's a more complicated issue than the NRA folks say it is...