“Are you going to say someone can’t be President of the United States because they have relatives in another country? “
Of course not. Certainly presidents may have relatives in other countries. The question is loyalty, and in Obama’s case, regardless of having relatives there, his Kenyan heritage is apparently very important to him (based on reports of his books), and IMO, this guy has spent his life trying to figure out his identity (and I don’t think he has solved it). IMO, that’s a little dangerous.
One attempt to prevent divided loyalties is the NBC clause. The NBC clause was one attempt to establish loyalty, but it doesn’t cover all possible situations of divided loyalty. Obviously, even an NBC could conceivably have divided loyalties, for their own reasons. A proper vetting process should turn up such issues in the case of an NBC, but a fawning media doesn’t lend itself to true vetting.
The point is, the issue is divided loyalty. The NBC was developed to help address the issue.