Cartoons have long been politically incorrect.

It was said that Helen of Troy had a face that could launch 1,000 ships. Now it can be said that a cartoon has launched protests and fatal violence around the globe.

Twelve cartoons published last fall in a Danish newspaper, and reprinted in other European media, including one depicting the prophet Mohammed wearing a turban resembling a bomb, have sparked protests throughout the Middle East, Africa and Asia. Islam forbids any images of Mohammed.

"Like any other art form used as a form of political expression, cartoons are just another medium, no different than the written word or a sculpture," said Stephen Kiviat, director of The National Cartoon Museum, which recently announced plans to move into the Empire State Building in New York City. "I wouldn't focus on the fact that it's a cartoon," he said, some thing that's been used as political expression for years.

He described the offending cartoon as "not out of the ordinary" for a political editorial cartoon.

"It's not different than ... hundreds of examples in the past to state a political position, or religious position."

Brian Walker, son of Beetle Bailey creator Mort Walker and a consulting curator to the museum, said most political cartoonists are satirizing and public figures are positioned for that type of criticism.

At the turn of the century, political cartoons attacked monopolies and political party bosses, always depicting them as big, fat, bloated pigs.

"I'm sure people thought at that time it was inappropriate, but it was justified because they were going after public figures," Walker said, adding that Thomas Nast's cartoons in the late 19th century led to the arrest of Boss Tweed.

During World War II, cartoons featuring Japanese employed intense racial caricatures. "It's almost embarrassing to look at that now. That was the enemy at that time, it was OK to make them look almost animalistic."

Though he has not seen the cartoon that has created the outrage, Walker called it "outside the realm of political comment. It's a matter of disrespect.

"It doesn't have anything to do with free speech."

About 10 to 15 percent of the museum's collection are editorial and political cartoons, including many from what Walker calls the "golden age": the Nixon presidency and Watergate era.

Political figures have been fair game going back to 19th century, he said, but the question seems to be, is a supreme being fair game? "Is that entity fair game for that type of parody?"

"It even goes beyond doing a political cartoon where you make fun of the Pope ... we have representations of Christ, God, the Pope, but that's not part of Islamic beliefs," Walker said.

He recalled a cartoon published last year by Pat Oliphant--described by The New York Times as the most influential cartoonist now working--called the "annual running of the altar boys."

"It definitely stirred up some emotions from the Church. It didn't pull any punches."

In any type of media, "there are certain kinds of prescribed rules that evolve over time," Walker said, and political cartoonists tend to have more room than comic strip cartoonists as they appear on a newspaper's editorial page.

"I think cartoonists are by nature always pushing the envelope, trying to get away with more or get more attention to a particular cartoon. It's more of a gradual process. When someone really steps outside the boundaries ... I think the reaction is way overboard, but I do think that there are certain rules of propriety or respect that exist in any cartoon medium."