Over the last few years I’ve heard this more often from my students: Federalism is problematic because if different states do things differently, they are unequal. Equality is taken to mean uniformity. The gist of the complaint isn’t that people in some states may bear greater burdens, or that they may participate less fully in the common good, but just that they don't all act the same way.
I find this view especially interesting, because in other contexts everyone sings the praises of “diversity” – but not in this case, in which diversity may actually count for something.