Leaning back in the coach section of an airplane demonstrates a basic lack of empathy. There's little doubt that leaning back two inches cannot create a position more conducive to comfort in a giant, flying metal tube. In fact, the only benefit leaning back in your seat on a jetliner actually warrants is peace of mind, as there is no such thing as a comfortable commercial airline flight (unless you're sitting in first class, which isn't "more comfortable" as much as it's "less uncomfortable"). 

A young girl sat beside me on a flight from Chicago to Phoenix today. The girl -- we'll call her 10E -- was probably in her middle-teens, sat beside a boyfriend, and had some sort of parental figure checking in on her regularly to see if she needed new magazines to read and to take pictures of her while she was napping. About mid-flight, just when everything seemed to be relatively normal, the woman in front of 10E laid her seat back. 10E is maybe a 100 pounds and quite possibly five feet tall, but the lay back of the woman in seat 9E was an obvious discomfort for 10E. Petite, mild-mannered 10E.

Fortunately for my teenage friend, she had seen the passenger in front of me lean back a few minutes before and 10E was able to observe my strategy: to wedge my knee in the center of the back of the chair in front of me.

Immature? I would agree if weren't for the fact that my knees have nowhere else to fucking go when my two inches of leg room turns into no inches of leg room. I, unlike 10E, am a big guy; well over the average in both weight and height. So my take is this: if you are knowingly making another human being uncomfortable, then you deserve a knee in your back. Maybe even a sneeze in your hair.