Sorry, did I say something different?
Blaming this stuff was an argument that was settled in the early 90s when parents of suicidal teens tried to blame heavy metal music for their deaths. It was a pretty landmark court decision. They should know better.
Stop thinking about the armed guards, that's also missing the point.
The point is security at schools is lacking, there are more ways to increase it than simply armed guards or police officers. It's sad that people can't see this. It's an opportunity to engage in open dialogue with the NRA, once you start talking it's possible to change their opinion on who should have access to firearms, who should not and maybe even what type of firearms.
A ban on semi-autos is unreasonable, with the exception of full auto or burst fire, the action is irrelevant. With a little practice you can fire a bolt action, pump action or lever action rifle with virtually the same speed as a semi-auto. Limiting magazine capacity is reasonable because it's feasible, they are easily pinned but what do you do about the thousands of high capacity magazines out there already? The best path is limiting access to firearms through licencing but as that goes against the very raison d'etre of the NRA they'll never support it. Tough for them, I guess. I'd be impressed to see Obama attempt something like that, it's not like he can go for another term anyway.