No, under normal circumstances, it is not. In fact, it is the opposite, as many dogs love to run around and chase moving vehicles like a bicycle. However, it can become cruel if the owner starts disregarding their dog's exhaustion.
Remember that you do not want to be dragging your dog around. If they get tired, the best practice is to let them rest for a few minutes before continuing slowly. Carrying a dog with you while you're riding a bike can also be dangerous, so avoid that as well.