"She could have used a knife."

After Christy Sheats shot her two daughters, a recurring argument from gun supporters was...

"Don't ban guns.  She could have just used a knife!  They could have been stabbed!"

Yes.  A lot of hypothetical situations could have happened.  But they didn't. 

Al Qaeda uses planes and shoes to create terrorist acts and we have tons of security put in place.  Hours of preventative measures... We even take our shoes off.

You know what people DIDN'T say?

"We don't need security because they could have just used knives."

The ability to kill via other means doesn't mean you neglect the way they DID kill.