Everyone has a right to go below the speed limit as long as they are going above the speed minimum.

True. But, in practice, it's quite dangerous to drive the posted minimum speed on interstate highways unless you're in a highly visible vehicle like a large truck or RV and have emergency flashers on. A passenger car or light truck going 45 MPH on a highway with a 70 MPH speed limit is a rear-end collision waiting to happen. I've been in situations where mechanical problems or heavy loads have made driving at or near the speed limit impossible, and I've rerouted to secondary highways. If I can't drive within 10 MPH of the speed limit on a "superhighway", I'll find a not-so-super-highway where being a slowpoke isn't a problem.