My wife got an inconsiderate parent/child combo back a few years ago on a flight from LAX-ATL. The young mother had a child about the same age as my two year old. My 6 year old and I had put up with him for quite some time. When he started throwing food over the seat towards us, I started to get irritated. My wife, in the seat ahead of me, realized what was happening and traded with me. The mother then stood the kid up on her legs, allowing him to bounce backwards onto the back of my 6 yr old's seat, repeatedly. My wife (she's so slick) timed the motions of the kid behind him and at the right moment, hit the recline button to bring my son's seat to the full upright position (it was only slightly reclined). This was enough to send the kid heading to the floor. He wasn't hurt but it stopped the ridiculous behavior. Oh, BTW, the older sister behind me had also insisted on kicking my seat back for some time, too.

So my opionion is...
The back of the seat, being part of the structure supporting your body is YOURS! Same for the lower portion, too. The tray table is not part of your seat.

As most of you know, the rules are simple. Don't do anything to the back of the seat in front of you that you wouldn't want someone to do to yours. Look before you recline and don't recline just to recline.

Remember, we're all in this (compartment) together. Show some respect and manners and air travel would be so much easier to endure.