Lyndon Johnson, in the sad later years of his presidency, was regularly hanged in effigy (as was Sarah Palin in the 2008 presidential campaign, by the way.) "Hey, hey, LBJ! How many kids have you killed today?" was shouted by demonstrators wherever he went. Johnson complained about the press that, "If I walked on water, the headline the next day would be 'President Can't Swim.'"The list goes on and on. Remember Harry Truman's advice that if you can't stand the heat, stay out of the kitchen.
Franklin Roosevelt was regularly accused of trying to establish a dictatorship and fascism in the United States. (Though to be sure, the word "fascism" carried far less sinister connotations in the 1930s, before the Nazi atrocities of World War II.) Eleanor Roosevelt's concern for blacks and FDR's willingness to appoint Jews to high office were the targets of a widely circulated racist and anti-Semitic doggerel.
Before modern political times, the level of insult was far higher still. John Adams called Alexander Hamilton "the bastard brat of a Scotch peddler." In the early years of the republic, newspapers made no pretense at being even-handed. Many were funded by politicians and parties to unashamedly advance their interests.
Even George Washington, twice unanimously elected to the presidency, found himself slandered in the press. The Philadelphia Aurora, the leading Jeffersonian paper, referred to him sarcastically as "Saint Washington," accused him of overdrawing his salary, and compared him to Nero and "a common pickpocket." By the end of his second term, Washington, like Johnson 160 years later, was desperately tired of being "buffeted in the public prints by a set of infamous scribblers."
Hmmm, I don't remember hearing these calls to change our behavior after a terrible shooting of a politician after Reagan was shot. No one was out condemning Martin Scorsese and saying that he shouldn't make the movies that he made even though it turned out that John Hinckley, Jr. was inspired by the movie, Taxi Driver.
The tone of political discussion today isn't something new. If you'll pardon my use of a statement originally meant for an actual war, Lincoln's attitude toward prosecuting war could also apply to politics: we don't conduct politics in this country "with elder-stalk squirts, charged with rose water."