But one ad at a DC Metro station -- which starts off criticizing Obama's health care reforms and ends up telling the president
to "go to hell" -- goes beyond the pale, says Jim Moran, a Democratic congressman from Virginia.

The advertisement is for "Sick and Sicker: When the Government Becomes Your Doctor,"
 a documentary that interviews Canadian doctors and patients in the hope of showing how dangerous "Obamacare" is for the American people.

"Barack Obama wants politicians and bureaucrats to control America’s entire medical system. Go to hell Barack," the ad says.

Moran wrote a letter to Metro general manager Richard Sarles calling for the removal of
 the advertisement.

"The ad is deeply disrespectful of the President of the United States and does not belong in
the Washington Metropolitan Area
Transit Authority (WMATA) network," he wrote.

It turns out that such language is within the accepted limits of American law and such advertisements are protected under
the First Amendment of the US constitution, guaranteeing free speech.

"WMATA advertising has been ruled by the courts as a public forum protected by
the First Amendment of the Constitution, and we may not decline ads based on their
 political content," the Metro authority said in a written statement.

"WMATA does not endorse the advertising on our system, and ads do not reflect
the position of the Authority."

Democrats have accused Republicans of lowering the tone of the political discourse in the United States during this election season, in particular with highly personal attacks on the president.

Arizona Governor Jan Brewer, a Republican, was widely condemned recently by Democrats for
 poking her finger at the president during an angry exchange on the tarmac after she greeted
 his arrival in Phoenix.

But conservatives argue that the treatment Obama gets is no worse than what liberals dished out
to former president George W. Bush, especially in his second term after the US-led invasion of Iraq