Obama has already stated that he was a dual citizen at one time (US and Kenya), though the Kenyan citizenship has lapsed. That can't be what he is trying to hide. In any event, I doubt any birth certificate in the US would list other citizenships held by the newborn.
Real Americans who love their country are not going to knowing vote for a President who is a foreign national or someone with dual citizenship. That persons allegience to this nation would always be suspect.
A majority of Americans voted someone who used to be a dual citizen into the White House. It's not an issue to most people, seemingly (certainly, it wouldn't have bothered me if McCain was a dual citizen).
You’re avoiding talking about the SCOTUS cases; why?
That is those people who have learned that there is a issue. Many are simply not aware of this issue due to the media blacklisting.