It really depends on how the word "hurt" is defined. A robot is defined as a machine that looks or acts like a human, and is controlled by humans. Firstly, to cause a being physical pain requires a nervous system, which includes the brain. Unfortunately, advanced as it may be, modern science has not yet artificially created a fully-functioning nervous system, never mind a brain. Therefore, although there are systems that could potentially respond to stimulus and mimic pain, at the present time robots cannot be hurt in the physical sense. To hurt a robot in the physical sense could only be achieved if the human nervous system could be accurately and very precisely mapped. And we are still a long, long way off from even understanding the entire purpose and potential of the human brain. Thus, it seems that not even robotics giant Japan could develop a robot that would feel pain, that could be physically hurt, any time soon. Of course, one must also take into account that should the nervous system be mapped and artificially reproduced, modern medicine would leap far beyond the need for robots at all. In fact, one could almost assume that that discovery could result in entire, living beings being created by mankind.
But in the other sense of the word "hurt," to "hurt" one's feelings if you will, requires the robot to "feel." It requires the robot to possess emotion. We do not know where emotion stems from and thus we cannot hope to recreate it in a machine. But how do we know, if we do not know of the origin of emotion, that we are not hurting any A.I? Plants are living things, and yet we do not know if they have emotion, or even if we are hurting them emotionally. The same can be said for robots. Any robot that bears any degree of intelligence could, by all assumptions, feel emotion or some artificial version of emotion. When we stimulate an intelligent machine by, say, giving it a command, how can we know that it is not begrudging of us? How can we know that we are not hurting its emotions by commanding it against its will if it should have one? Because it is not programmed to feel emotion? Plants do not have ears and yet some say they react to our words. They cannot understand our language and yet some say they react to kindness and encouragement. Robots cannot understand us; they cannot interpret what we are saying. When is it possible to hurt a robot? Whenever we deal with intelligence, we are dealing with the potential for hurt. That is when it is possible to hurt a robot: when it becomes aware.