I am one of those people who stands up right away (I am always in an aisle seat, for several reasons) but I am very careful not to jostle others, because it does indeed bother me when people do it to me. If I can’t reach my bag in the overhead without pushing through people to get to it, I wait until it’s my row’s turn to deplane—you’re not going anywhere for a while anyway, so why do you need your rollaboard down instantly? This always bugs me. I also definitely turn around and say something if someone is pushing me from behind, which happens from time to time. An assertive “You are pushing me. Please stop” works. You don’t need to start a fight, but you do need to firmly make your point without leaving room for them to argue with you.