On Monday my wife and I flew EWR-RSW . Occasionally when the economy fare is cheap we will buy an extra seat for comfort . As I began to scan the boarding passes I was questioned by the gate agent . In a confrontational tone she asked "Why do you have to have an extra seat " . We are not overweight and I politely told her we like the extra room with an empty middle seat . She then responded " Well you know you can't lift the arm rest in the exit row " . It was unprofessional for her to speak to us in that manner and we don't think anyone should be questioned about an extra seat purchase let alone in the manner that she did . Gate agents should welcome you onboard, not grill you .