This is the vexed question which plagues the cattle class passenger- is it rude to recline?
What if someone else does it- don't you feel you have to then relcine yourself to regain your level of space- and then the guy behind you thinks the same and so it goes on?
Personally, I don't recline, as I think it must be awful if the person behind me is long-legged or fat, or if they want to keep their traytable down after the meal for whatever reason it would be very awkward for them. But then I am quite lucky in that I can sleep upright if needs be.
I don't really get the rage if somebody in front does it to me, as I am very wee and it makes fuck all difference to my knees whwether the seeatback in front is ten incheds away or 15 (it did annoy me once though when somebody reclined when I was still trying to eat a scone and drink some hot tea!)
I think the only time it's excusable is on an overnight where they put the cabin lights off, and you're kind of half expected to recline and snooze so that the cabin crew can go and do a few lines of coke and spray themselves with estee lauder off the trolley, ready for breakfast and landing.
It was this that made me think of it-
(apologies for DM link, don't know how to use that indirect traffic router thing)