Let's take a little travel back in time, shall we?
It's 2006: George W. Bush isn't any closer to finding Bin Laden than he was in 2001, the housing bubble ruptures, the US military is still getting in trouble often for torturing, raping, and murdering civilians in war zones, gas prices are rising, and Bush is protecting the wealthy by pushing for privatization of social security and other government functions.
Liberals are pissed. They criticize Bush, call for impeachment, call him a liar, cast vicious stones at him using words like "murderer" and "criminal" and "jackass" and "moron". Conservatives pull the patriotism card, accusing Bush's critics of "hating America" and "constricting freedom and what makes this country great", saying that ALL Americans should respect the President because of the office. End of story.
Let's return now to 2010.
Barack Obama is losing popularity and his agenda is slowing unraveling before his eyes, while the US trade deficit increases, the economy remains stagnant, unemployment is about 10%, political favor for healthcare reform is slipping away, and Iran/North Korea are posturing against what they perceive is a weak administration.
Conservatives are pissed. They criticize Obama, call for impeachment, call him a liar, cast vicious stones at him using words like "socialist" and "pro-abortion" and "inexperienced" and "Nazi". Liberals use this bile to attack the upper class to position themselves as "defenders of the common man", while conservatives say Obama is actively trying to destroy America from inside out and he's a traitor and sometimes imply that he is actually a secret operative from an anti-American organization (that somehow managed to sneak him into the country, get him through Harvard, into Senate, and elected president, all without having the secret plan discovered).
If George W. Bush deserved respect because he was President, then so does Obama. The very same people who were critical of Bush's attackers are now attacking Obama in similar ways and not seeing the hypocrisy.
Either the President deserves to be respected REGARDLESS of politics, or not at all. You can't set "rules" that have arbitrary standards for which Presidents are to be expected.