I would argue that we should not condemn the use of drones in warfare. They do not make warfare any more inhumane than it has to be. In fact, you could argue that the use of drones is a positive good because it can reduce the risk of death that the pilots of "manned" aircraft face. In addition, you can argue that the operator of a drone is less likely to make mistakes because he or she is not moving as fast and is not in a life or death situation.
The best argument I can think of against the use of drones is that it exposes one side to being killed without being able to have any chance of fighting back. This gives a huge advantage to technologically superior forces and can be said to be a way of using technology to oppress less developed people (just as guns or cannons or ships were used by Europeans to oppress weaker people in the age of imperialism).