That more people are for or against a particular president has no relevance as to the correctness of that president's actions. Most people in Germany were for Hitler. Most people supported Nixon until the last couple of years. Most people voted for Hillary.
The fallacy is argumentum ad populum (also known as appeal to democracy!).  Sure, we use popularity (mostly) in our elections, but even the majority can be wrong. Hopefully less so than the minority.
But the Framers knew this and established rights that would be very hard for the majority to deny. To deny certain rights the Constitution would have to be changed. That is hard, and by the time it reaches a vote, the passion for change often wanes. Still, mistakes can be made, as in Prohibition. 
It's an interesting read: https://en.wikipedia.org/wiki/Argumentum_ad_populum