I just can't believe the bad attitudes being expressed here. regardless of whether you are on a plane or not, how about just being nice to other people.
The original poster knew his seat recline caused the passenger behind discomfort, so don't recline. Simple. Some people don't ask politely initially, because they just don't have the communication skills, and find any situation like that difficult to deal with. The fact the passenger was over weight is pretty irrelevant, do you know why the person was overweight? there are many possible explanations, including medication, cancer therapy, metabolic imbalance. Not everyone who is overweight eats donuts all day long, but even if they did it is NO EXCUSE for sh*tty behaviour. Everyone has faults.
Most of what I have seen in this thread is based around petty prejudices, and an "I don't give a **** about anyone else" attitude. Jeez, what is up with you people.
Try being nice to people, it really works, and is a helluva lot less stressful. It also means you don't need to ask silly questions about whether or not you should recline your seat, as the answer is pretty bl***ing obvious.