I find it hard to believe that you qualified your statement with a "once the whacko dispatched the teacher" which supports my argument that killing 28 people with a machete is harder than it is with a gun but you still decided to start name calling.
Even though I'm sure you have given this some thought, I am afraid that you still have not grasped the full extent of the problem, violence is not a simple issue that you can just attribute to one cause (over abundance of whackos), and having easy access to guns and very little deterrent to using them most definitely increases violence.
Yes, better gun regulation will not stop massacres everywhere instantly (nothing will), but it will help reduce the problem. And yes, knife registration would further reduce the problem, as would putting everybody in protective spheres and banning all human contact, but those solutions are not practical, which is why you won't see a lot of people lobbying for those.