Dave Weigel notes something different about this particular act of political violence—they're attacking  the First Amendment rather than the Second:

Giffords and Guns
Posted Saturday, January 08, 2011 7:06 PM | By David Weigel

My friend Matt Zeitlin pointed out today that, in another era, the Tuscon shooting would spark a discussion about gun rights, not political rhetoric.

Oh, yes, it did.

Here's libertarian L. Neil Smith explaining why and how he joined the NRA.

I'd been in Junior NRA as a Scout, but the course of my life had taken me away from shooting (it seems hard to believe now) until just before that surrealistic year of 1968 when, as a newly-fledged handgun owner (we'd had an incident in the neighborhood) I recall sitting in front of the TV watching the assassination of Bobby Kennedy, knowing the proclivity of liberals to blame everyone but the perpetrator, and thinking, "Boy, we're gonna get it now."

And so we did.

That was written in 1995—things are better now for gunowners.

Weigel goes on:

Worth noting: Giffords was a staunch supporter of the Second Amendment, and a gun owner. She signed an amicus brief in support of the D.C. v. Heller, the case that overturned Washington, D.C.'s gun ban.

Giffords is a pro-immigration Democrat, but she's also an Arizona politician. The fact that this is her position shows how far the debate has shifted since 1968 or even 1995.

It's possible the immigration debate will shift the same way