Are there any stats on how many times the extra firepower afforded by automatic weapons and large magazines actually made a difference for self defense vs. making unlawful killers so much more efficient at the task?
I know these weapons are out there, but if there is a will to put the genie back in the bottle (maybe not the hopeful analogy), there will be a way to do it even if it takes a long time. But you gotta start some time. I wouldn't necessarily be opposed to grandfathering qualified individuals (would need checks on eventual transfers; e.g., at death). No, a ban wouldn't stop a sophisticated and determined terrorist or criminal, but it would make it more difficult for average criminals and psychos to get their hands on the weapons. Who are you more likely to be up against?
I can appreciate that you're trying to approach this reasonably. But perhaps solutions can be approached a little more cautiously -- where are current societal and cultural trends taking us, both domestically and globally? What issues are really at hand? What are the long term implications of a course of action?
To what extent should a non-perfect government restrict the natural rights of a populace and to what end? We're not talking about privileges here; please consider the differences between a natural right and a privilege. We're so lax with with abuse of privileges but oddly strict on natural rights. This does not bode well for society. When you have a biased media, one should be extra diligent with the cause they are advocating.
But in the end, one reaches their individual decisions through whatever process one deems appropriate.