Certainly the rights embodied in the United States constitution and bill of rights are in place precisely so that they are not subject to the whims of populism. However, for certain policy decisions, whether or not the proposed policy sits well with a majority of citizens can be helpful for decision makers.
Populism has a long history in the United States, and much of it is positive. Many of the rights and social reforms we take for granted are the result of populism, and in a time of ever growing inequality and gentrification, America is due for some populism. It has its drawbacks, but it has more positives.