The latter statement, (not that I mean to sound like a washed-up militiaman), is very similar to what was said about the British military during and before the American Revolution. As for the record: Let's look at it. Vietnam: we went in and our military was defeated by a band of guerrillas. Even right now, in Afghanistan and Iraq, our impeccable and indomitable military is making little progress against Afghani and Pakistani guerrillas and against Iraqi insurgents. Horbinski discusses the use of assault weapons, by which I assume she means firearms capable of firing fully automatically (known legally as machine guns).
These weapons are very heavily regulated and, in order to legally possess one, you must submit to a long and arduous process which will strip you of some fairly basic Constitutional freedoms and which will leave your wallet (or purse) much, much lighter. Suffice it to say that most criminals who want fully automatic weapons do not get them this way; they tend to get them from the black market, where there is no government control, no rights are given up and the guns are significantly cheaper.
The key to controlling the use of assault weapons would be to step up efforts to prevent firearms from being sold illegally, including prosecuting those who violate federal firearm laws (which no president has done). The problem does lie with "the idiot that's pulling the trigger," but so long as that idiot wants to pull a trigger, he or she will find one to pull, no matter how many guns are banned. And in banning more guns, we make it less likely that someone will be able to stop that idiot after they draw their weapon and before they can do real and lasting damage.
In closing, our military is not all that and a bag of chips, Uncle Sam does not always get his man and, to use the cliche, "If guns are outlawed, only outlaws will have guns."