Just because something is a bad idea doesn't mean it is contrary to the Constitution. In fact, most bad ideas are perfectly constitutional. In such cases, the best way to prevent bad ideas from becoming reality is to use the ballot box. So if someone running for president is a current active dual citizen of another country, the best way to keep him from becoming president is to vote against him.
Not that any of this applies to Obama, who he lost his dual citizenship with Kenya nearly 30 before he ran. Furthermore, he was never an active dual citizen, in that he never held a Kenyan passport, never voted in their elections, etc. I still voted against him, though, for other reasons.
I'd also say that I wouldn't hold dual citizenship against a candidate who is a current dual citizen, but who never acted upon it. For example, Italy recognize first-generation US-born Italian-Americans as dual citizens. If such a person never bothered to get an Italian passport and never voted in an Italian election, I most certainly wouldn't mind if such a person became president.
As I already pointed out, I would argue that Obama’s trip to Kenya whereas he illegally violated the Logan Act and actively was involved in campaigning in the Kenyan election was an affirmation of his loyalty to Kenya as a dual citizen.
And I did not claim that my statement about using common sense was a means to determine the Constitutionality of the term ‘natural born citizen’ but was simply pointing out that the definition that many argue is the correct legal one also makes complete common sense as well.