President George Washington would bow to guests at presidential receptions to avoid physical contact and the tradition lasted through the presidency of John Adams. Washington would rest one hand on a sword and the other holding a hat to avoid the remote possibility of anyone forcing a handshake! Thomas Jefferson ended the tradition of “bowing” by shaking hands when greeting people (ConstitutionFacts.com - Learn about the U.S. Constitution, the Bill of Rights, the Declaration of Independence and much more!).
But seriously, though...getting riled up over the President bowing...
The Makeout Hobo is real, and does indeed travel around the country in his van and make out with ladies... If you meet the Makeout Hobo, it is customary to greet him with a shot of whiskey and a high five (if you are a dude) or passionate makeouts (if you are a lady).
I don't think that people actually care about the bowing. They are just looking for anything to bash Obama. In many ways, these people are nearly identical to people who bashed Bush for the pettiest of reasons. America would be better off without them.
"If your opponent is of choleric temperament, seek to irritate him." - Sun Tzu