It really isn't. That's a heavily controlled environment. Airlines condone reclining. Therefore, reclining should be expected by people paying to enter, unless the terms of service state otherwise.

The only idiotic part of this equation is the person who misdirects intolerance and anger at the recliner rather than at the airline's environment. On an individual level, money is one form of compensation to give up a feature one would expect to use. Asking to be paid isn't the same thing as expecting to be paid. Try negotiating with honey (dialogue), not vinegar ("Knee Defenders"). Or pay up. Or boycott the airline. Use something else. Air grievances.