To be fair, not all of the "common sense" is a characterization of gun regulation proposals. Here's "Parenting common sense and solace," for example. And here's one referring to "the common-sense procedures" that schools can put in place — and that in fact were in place at Sandy Hook Elementary School. But most of them seem to be about "common sense" gun control.
Why is "common sense" the meme of choice?
1. The massacre itself feels senseless, and we want things to make sense. Our fervent desire for sense about what happened in the past makes us amenable to related ideas for making sense. Politicians and policymakers step forward to fulfill/manipulate this need for meaning.
2. To say that this "sense" is "common" is to say: a. It's easy, relax, and see what is right in front of your eyes, and b. This conversation is over, and only weird/bad people are cluttering it with other ideas. "Common sense," by offering closure and comfort, seems well-meaning and helpful, but it is also manipulative and power-enhancing.
3. "Common sense" says: I'm moderate. I'm not about banning and confiscating guns, but doing a few modest things that will constrain the bad people of this world without burdening the good people (like you). In that, it's similar to "balanced approach," which is getting a workout in connection with the "fiscal cliff" negotiations. Those who want more taxes — only for the bad guys, not for you! — want to look sensible and moderate. It's those other people who are unbalanced.
4. "Common sense" is a quintessentially American frame of mind. It was the title of the pamphlet Thomas Paine wrote in 1775, stirring up revolutionary fervor. It was completely incendiary and treasonous. And it led to quite a bit of gun violence.
There were those in high places who, while in agreement with Paine's sentiments, voiced criticism of his method. John Adams, ... in his Thoughts on Government wrote that Paine's ideal sketched in Common Sense was "so democratical, without any restraint or even an attempt at any equilibrium or counter poise, that it must produce confusion and every evil work."Ah! So balanced approach has deep roots too. We are a pragmatic people, and we like practical proposals. We're amenable to arguments framed as balanced and common sense. But if we are indeed practical, we know these are propaganda words, and we look on them with suspicion.