I agree that the clause seems unfair, but if you try to put yourself in the mindset of the founders, it's actually a challenging problem. What makes someone an American? It was clear that it is not ethnic identity and it's not where your ancestors are from, which were the main options prior to the founding of the US.

Also, do be aware it was created with people in the room who were aware of its consequences. Alexander Hamilton signed the document that made it law, and it prevented him from becoming President.

http://en.wikipedia.org/wiki/Constitutional_Convention_%28Un...