Every American student who's taken a civic class has heard US Supreme Court Justice Oliver Wendell Holmes, Jr.'s admonition that free speech under the US Constitution doesn't give you the right to shout "fire" in a crowded theater.
So the right to bear arms under the 2nd amendment - - written at a time when citizen militias might be needed to fend off the British or a foreign power intent on undermining the new Republic - - shouldn't mean someone has the right to barge into a crowded theater, open fire and slaughter people with powerful guns and ammunition obtained legally.
Yet we have allowed the NRA and allied wealthy conservative organizations with political and electoral agendas to distort legitimate gun ownership for hunting purposes into gun ownership without effective controls that jeopardizes public safety.
Bill Moyers has an eloquent essay about this, here.
The proof is the disproportionate share of the industrialized world's gun violence that afflicts the US, year-in and year-out.
These massacres bring concern for victims, but no remedial controls: the Aurora shootings come but five years after a higher death toll in a mass shooting at Virginia Tech, and Colorado did not toughen its gun laws after the Columbine school killings not far from Aurora.
Few political figures in either party will take on the NRA. We've got bi-partisan political cowardice, and the result is gun access for lunatics.
We need a mass movement along the lines of Occupy Wall Street to get things started towards reasonable controls on gun ownership, or we're only closing in on the next Aurora, let alone the less-publicized daily gun mayhem happening across the country.