We're not. Biden's Secret Service code name might as well be "Poison Pill," as far as that goes.
But, there are future consequences, arising from allowing this to go forward unchallenged. Think of potential, worse, presidential candidates, that could be allowed as a result of precedent.
That is why the more stringent "natural born" eligibility requirement is there, to ensure a President who actually identifies with and cares about his or her own country. The requirement has never been tested in a court of law. Obama will be the first, assuming at least one of the many plaintiffs is found to have standing.
Very historic.