James Pierson, in his book Camelot & the Cultural Revolution: How the Assassination of John F. Kennedy Shattered American Liberalism, points out that pundits were writing things like

"The irony of the President's death is that his short Administration was devoted almost entirely to various attempts to curb this very streak of violence in the American character.

When the historians get around to assessing his three years in office, it is very likely that they will be impressed with just this: his efforts to restrain those who wanted to be more violent in the cold war overseas and those who wanted to be more violent in the racial war at home.

He was in Texas today trying to pacify the violent politics of that state. He was in Florida last week trying to pacify the' businessmen and appealing to them to believe that he was not "anti-business." And from the beginning to the end of his Administration, he was trying to damp down the violence of the extremists on the Right."

Why America Weeps: Kennedy Victim of Violent Streak He Sought to Curb in the Nation By JAMES RESTON, Special to The New York Times, November 22, 1963

Reston doubled down on the "we're-all-guilty" stuff in

A Portion of Guilt for All; New Violence Underlines Need to Fix Public as Well as Private Responsibility 'We Have All Had a Part' By James Reston The New York Times, November 25, 1963

This was in spite of the fact that reporters, rather than pundits, at the Good Gray Newspaper of Record were actually reporting that  Oswald was, in fact, a Communist:

MARXISM CALLED OSWALD RELIGION; Suspect 'Refused to Eschew Violence,' Friend Says Oswald Lived Alone Carried 'Camping Equipment', By Donald Janson,The New York Times, November 24, 1963

So we would only be "all guilty" if we were all Communists. In the Giffords attack we would only "all guilty" if we were all schizophrenic.

This is mentioned in   "Steering The Coverage", a video on media and the Gifford shooting, in which Ed Driscoll says that "For anyone who was on Twitter at the time the news first broke, it was quite a sight watching old media’s narrative emerge in real time even before any of the basic facts of the story were known." (Via Kathy Shaidle.)