Guns and not inherently a Right-wing issue - self-defence against jackbooted thugs has plenty of Left appeal. The main bone contention is not about gun control (I think every rational person agrees that a system allowing tracking every weapon to its rightful owner is a good thing) - but about life styles. Gun has become a symbol of of the white-rural-or-suburban-male-I-wanna-do-what-I-want-damn-it life style. It is because of its cultural connotation rather than the utlity of the thing itself that guns have been embraced by rednecks and rightwing trolls and abhorred by the progressive types.
As to the DC sniper - the Left does not want to discuss this issue, because anything that can been said about this specimen would not be nice and politically correct (IMHO people like him should be publicly executed, which means, yes, full support for death penalty for violent males, thank you) - and that would mean addressing tough issues in a non-doctrinnaire way, which many Leftist would rather avoid.
Wojtek