Ok, but that does not give the employee the right to be rude. A simple remark such as "I'll pass that up the chain," or "an email to customer care would be the best way of suggesting this to management," would be polite and would save the agent the hassle of having to explain to a customer for the umpteenth time that the agent has little input into the kiosk interface design. I realize that there are plenty of rude customers out there who treat frontline employees with disrespect, thereby causing employees to become jaded. Such customers make life difficult for employees and polite passengers alike. "Sometimes you win, and sometimes you don't" is not an acceptable attitude with respect to frontline employees, however.

Certainly, an agent cannot expect a passenger to read his or her mind. For example, when a pax makes a suggestion such as this, the agent very well may be thinking, "you f*****g idiot, I've had to listen to whiny pax and stupid suggestions that I have no power to implement all freaking day! Can't you get it through your thick skull that it is not my job to ruminate with you about the nuances of the kiosk interface all freaking afternoon!" But, because running an airline is a customer service business, it would be inappropriate to state this outright. Instead, a simple "That's a good idea, I'll pass that along," or at least some other acknowlegement of the customer's concern, is warranted. To me, an agent who acts in the manner described by the OP (assuming polite behavior by the customer) is no different from a rude pax whining to a gate agent or FA about some trivial matter. The fact that frontline agents may have a tough job in dealing with people is not an excuse to become jaded.

If anything, the agent's behavior was self-deprecating. Behaving in such a manner is akin to saying, "why would you suggest that to me, I'm a lowly CSR and my opinion doesn't matter worth a damn to this company."