Potato bread is chometz gamur. It has wheat flour in it.
There are numerous reasons given for the issur of kitniyos, and based on the different possibilities, there is often a a machlokes whether a particular item falls under the category of kitniyos.
It’s a somewhat complex halachic matter. The issue here, which I believe the OP is alluding to, is that some people are expressing opinions based on sociological factors rather than halachic.
Sure, they’ll make it sound halachic, but these people wouldn’t express their opinion on some complex issue in hilchos taaruves, yet have no problem when it comes to kitniyos.