"Shut up," they explained
It would be interesting to do a Venn diagram charting the intersection between people spewing hate at the Pope, people with "COEXIST" bumper stickers on their cars, self-professed fans of left-wing maniac Chris Dorner, and those who think Dr. Benjamin Carson was unforgivably "rude" to Barack Obama by daring to dissent from his ideology at the National Prayer Breakfast. I suspect considerable overlap between those groups would be revealed.
The "Carson is rude" meme gathered strength after a few prominent liberal pundits tossed it out there, and the gears of Twitter began churning. It's one of the lamest non-responses I've ever seen - a fairly frank admission from liberals that they have no substantial response to Carson, so they'll question whether it was appropriate for him to pipe up at all. Never mind that Obama has used such occasions, including a previous National Prayer Breakfast, to expound upon the alleged Biblical support for socialism.
And of course, an eloquent liberal who made, say, George Bush visibly squirm in his seat during such an event would be hailed as a great hero by the same people who think Carson was disrespectful to Obama. The religious illumination of ideology, and public dissent in the presence of high officials, are tools meant to be reserved to the Left.