Right wingers have repeatedly -- and nearly explicitly -- called for such assassinations. They are now saying they have no responsibility for this event because the shooter was mentally unbalanced. I don't know why anyone would expect any logical thought from them on the issue: for example, realizing that calls for assassinations are likely to be first heeded by the mentally unstable. I hope that responsiveness to their rhetoric doesn't spread to the slightly saner tiers of the population.
A large number of commentators have expressed their horror and fears for the future much better than I can. For example, Paul Krugman concluded his NYT column today thus:
"The purveyors of hate have been treated with respect, even deference, by the G.O.P. establishment. As David Frum, the former Bush speechwriter, has put it, 'Republicans originally thought that Fox worked for us and now we’re discovering we work for Fox.'
"So will the Arizona massacre make our discourse less toxic? It’s really up to G.O.P. leaders. Will they accept the reality of what’s happening to America, and take a stand against eliminationist rhetoric? Or will they try to dismiss the massacre as the mere act of a deranged individual, and go on as before?
"If Arizona promotes some real soul-searching, it could prove a turning point. If it doesn’t, Saturday’s atrocity will be just the beginning."