ATL - HPN Strange flight encounter with another passenger... AITA?

Let me paint a picture here: a few years ago, my wife, sister, and I were on a flight from Atlanta to Westchester. My wife and I scored First Class upgrades, but since my sister had never flown First Class before, I thought I’d be a decent person and let her enjoy the experience. So, I sat in her Comfort seat while she took my original First Class seat.

Now, this wasn’t a standard plane; it had a smaller layout with a 2-1 seating configuration, meaning there was no room to stow my bag in front of me. No overhead space was left in Comfort, so I placed my small carry-on in the overhead bin near my original First Class seat—a logical move, right?

Enter this guy. Not ten seconds later, a passenger from a few rows back decides he’s going to yank my bag out, leave it sitting in the middle of the aisle like discarded trash, shove his own bag in its place, and sit down as if nothing happened. Stunned, I politely explained the situation to him, and what does he do? Shrugs, puts his headphones on, and acts like my words are an annoying buzzing in his ear.

How hard is it to show a sliver of courtesy? Since when did basic respect become too much to ask? Honestly, what is wrong with people these days?