If your vehicle has a manual transmission, using cruise control while towing is fine. If it has an automatic transmission, it will drop into a lower gear when going up hills, which puts wear on your automatic transmission. In both cases, while towing I will use the cruse control but I will manually accelerate when approaching a hill so that I can decelerate a little while I am going up the hill. With an automatic transmisson this will keep it from hunting or dropping to a lower gear.
As long you can keep your Silverado from shifting gears a lot while you go up hills, it is okay to use cruise control while towing. If you routinely forget to accelerate as you approach hills, you might be better turning it off.