People lose all sense of etiquette and sensibility when they are in an airport.
1) Standing in line to get to a preassigned seat.
2) Pushing people around to fit your carry-on in the overhead.
3) Standing up immediately when the plane reaches the gate and cutting in front of other people.
4) Listening to absurdly loud music on shitty headphones
5) YELLING at airline employees about weather delays or other issues. You can be mad without letting the entire airport know what issue you are encountering.
6) Loudly complaining about TSA agents doing their job. It's like people forget 9/11 ever happened.
7) Putting a sweater or some other item of clothing in an overhead bin (unless it is on top of your own bag)
8) Trying to put huge bottles of liquids in your carry on and then complaining that TSA is making you throw it away.
Anyone who reclines their seat on a domestic flight deserves any abuse given to them. It makes traveling 5-10% more comfortable. So basically not even worth it considering how douchey it makes you look. I don't really have a problem with it on international flights but only if you are sleeping. If you are reading or watching a movie you better have that seat upright.
I've been on flights where people will recline their seat BEFORE takeoff, unrecline it for 2 seconds when the flight attendant tells them to, and put it right back when after the attendant walks away.
On the shoes topic, I think it's fine to remove your shoes on an international flight or coast-coast flight, but you must be wearing socks.
By the way, the fact that airlines have not yet figured out that they should seat people from the back of the plane to the front blows my mind.