I can understand if locals want elections and local government to serve the people who are permanent residents of the area, rather than weighted by a large population of temporary students who will have moved away in a few years time.
When it comes to college students, if you're talking about state-wide elections it all evens out anyways, for every college student that has come to a state, there is a college student who has gone out of a state. Instead of being a Democratic vote in your temporary college town, you are a Democratic vote in your former permanent residence. A Democratic vote is a Democratic vote.
The way progressives, and even you, tend to portray things is as if half the population of the U.S. has this deep resentment towards "the other side", which I just don't believe is true, thus I tend to believe alternate possibilities more than the "I want the other side suppressed" theory.
Many progressives do hold the belief that conservatism is primarily about racial oppression, thus they naturally believe these reasonings to be true.