One objection to this idea is obvious: where's the counter-evidence? If he wasn't born in Hawaii on August 4, 1961, where was he born? Birthers, of course, will answer that the fact there is no evidence of him being born somewhere else is just proof of a very effective conspiracy of silence.
It seems utterly illogical for millions of people to dismiss clear and obvious physical evidence of such a simple fact. But there is a certain reasoning behind it. Twisted and bizarre reasoning, but reasoning nonetheless.
One of the basic problems with American democracy is that every four years, a new president is elected who has been chosen by a large chunk of the populace, but who has also been rejected a large - but (usually) smaller - chunk of the populace. So the people who rejected the president have to deal with the fact that their understanding of reality clashes with that of tens of millions of their friends, neighbors, and fellow citizens. This requires some occasionally painful mental adjustments. The most difficult such adjustment led to the Civil War.
Liberals have had a particularly difficult time of this of late. From for the 40 years from 1968 to 2008, a Democrat occupied the White House for just 12 years. Democrats developed what was, for me, an unfortunate coping mechanism. It usually boiled down to a simple phrase: "The American people are stupid." Ronald Reagan and the George Bushes, particularly the latter one, were not great men, and Reagan and W were not very bright. The only kind of people who could vote for someone stupid like this must be stupid themselves. But they were elected by a majority of the American people (except in 2000). Therefore the American people must be stupid.
That idea seriously rubbed me the wrong way for a long time. I don't like intellectually condescending attitudes like that because they're obnoxious and wrong, but also because they are highly counterproductive politically. It just doesn't work all that well to say to someone "You're really stupid, would you please consider voting for my candidate or supporting my cause?" This is why Democrats developed a reputation for being arrogant elitists.
As unfortunate as that attitude may have been, at least it was within the bounds of normal political discourse. It may be disrespectful to dismiss a whole class of people as beneath you intellectually, but at least it's not completely deranged.
The birthers are rational in their own way. The problem is that they won't admit their reasonings, because they're deeply offensive. A fair amount of this reaction, if not most of it (or all) can be attributed, in my opinion, to racism. Certain people just don't want to admit that a black man is president. Casting doubts about his legitimacy is a way of expressing fundamental opposition to his presidency without looking like you are racist. The fact that the circumstances of Obama's birth - a foreign father, a young mother, born in the newest state, literally on the geographic fringes of America, both parents dead, an interracial marriage at a time when that was illegal in many states, no other children from that marriage, which dissolved fairly quickly, and then a childhood spent in a Muslim country - Indonesia - that most Americans couldn't find on a map. Most unfortunately, for Obama, the details of his birth, parentage, and childhood play into conspiracy theorists' hands almost perfectly.
What must drive the birthers absolutely nuts, however, is that for members of Generation X, Obama's history isn't all that unusual. A romance between an American and a foreign exchange student? The details may be different, but I doubt there is a teenage boy in America who hasn't been intrigued by a girl in his high school/college/hometown with a foreign accent (for the cinematic version, see Shannon Elizabeth in American Pie). Years spent in a foreign country? That goes on the resume. It's also great cocktail party conversation. All of the things that make Obama a foreigner, strange, "other," for the nutjobs on the rights are accidents of birth that make him cool for Generation X, Y, the millenials, and the hipper Boomers.
For the GOP, the "birthers" represent a major problem. This is an excellent example of my Assholes and Idiots Theory. Leaders in the GOP are completely failing to contain these people. It's just not a good idea to let complete lunacy infect a party trying to come up with anything resembling a coherent governing philosophy.
At some point, some Republican leader - or at least some Republican elected official - is going to have to stand up to these folks. My suspicion is that it will be one of the senators from Maine, Susan Collins or Olympia Snowe. They're both moderates, so they have room to alienate hardcore conservatives. At least they're moderates in today's GOP. They're both fairly secure in office. As Republican women senators, they are familiar with being slightly outside the political mainstream. They represent a very old state, with deep Yankee traditions. There would be a certain geographic irony of either of them defending the birth of someone born as far away as possible in the U.S. from their state.
It might be John McCain. He, after all, had his own issues with being eligible for president because of his birth - he was born in the Panama Canal Zone (to American parents). He's still got that whole "maverick" thing going on, occasionally. It could be a matter of honor for him to defend the man who defeated him.
Somehow or other, these people have to be contained.