Comedian Wanda Sykes pulled no punches as she skewered conservative talk show host Rush Limbaugh at the  White House Correspondents' Dinner -- but her morbid cracks set some guests' cringe-meters off the charts. 

Sykes accused Limbaugh of treason, compared him to Usama bin Laden and wished for his physical collapse as she roasted the favorite target of liberals Saturday night at the Washington Hilton.

"Rush Limbaugh said he hopes this administration fails, so you're saying, 'I hope America fails,' you're like, 'I don't care about people losing their homes, their jobs, our soldiers in Iraq.' He just wants the country to fail. To me, that's treason," Sykes said. 

"He's not saying anything differently than what Usama bin Laden is saying," she continued, before addressing the guest of honor, President Obama. "You know, you might want to look into this, sir, because I think maybe Rush Limbaugh was the 20th hijacker. But he was just so strung out on OxyContin he missed his flight." 

The crowd groaned, Obama smiled and Sykes may have noticed a little discomfort in the room.

"Too much?" she asked. 

But then she piled it on: 

"Rush Limbaugh, 'I hope the country fails' -- I hope his kidneys fail, how about that? ... He needs a good waterboarding, that's what he needs." 

Obama joined the crowd in laughing at the crack about Limbaugh's "kidneys."  

But White House Press Secretary Robert Gibbs suggested Monday that Sykes' bit was considered in poor taste. 

"I don't know how guests get booked," Gibbs told reporters. "I haven't talked to the president (about it), but my guess is there are a lot of topics that are better left for serious reflection, rather than comedy -- I think there's no doubt that 9/11 is part of that."

After the appearance, conservatives bellowed that Sykes was way over the line. "Mean-spirited," "hateful" and "disgusting" were just a few of the words used by conservative bloggers and commentators to describe the performance. 

"This woman comes up and says, 'I hope Rush Limbaugh dies,' and everybody giggles," said Tim Graham, director of media analysis with the Media Research Center. 

National Review columnist Jonah Goldberg called it "particularly awful." 

Sykes' publicist was not immediately available for comment.

Some critics said there was a double standard employed for conservative and liberal jokesters, pointing out that golf announcer David Feherty apologized over the weekend for his column in which he joked about U.S. troops wanting to kill House Speaker Nancy Pelosi and Senate Majority Leader Harry Reid. 

Feherty's line drew heavy attention from the liberal group Media Matters and earned him a "worst person in the world" dubbing by MSNBC's Keith Olbermann. 

Graham said the relatively low-key coverage of Sykes' joke in mainstream media underscores the "slanted take on what's hateful and what's not." 

"When a conservative says it, it's an utter outrage. And when a liberal says it, it's a knee-slapper," he said. 

An editor with Britain's Daily Telegraph who was at the dinner wrote that liberals will give Sykes a pass, since her target was a right-wing talk show host. And he marveled at Obama's response. 

"That's way, way beyond reasoned debate or comedy and Obama's reaction to it was astonishing," wrote Toby Harnden. "Imagine if a comedian 'joked' that Obama was a terrorist who was guilty of treason and should be tortured and allowed to die. There would justifiably be an outcry."