It's true enough, but doesn't really matter. A lot of people know Clemson as a pretty good school, but just don't know where it is.
Having been outside of the state for more than a generation, I see how people can view the states of South Carolina, Louisiana and Mississippi as basically the same - last or next to last in education, poverty, health care, etc. Clemson doesn't fit the stereotype people have for SC and the other poorer states. I was shocked at a conference in SD a few years ago when a speaker brought up the "corridor of shame." Hopefully the perception is slowly changing, but the tea-bag mentality in that state is really holding it back.