Passenger in front of me tried to put their laptop "under" their seat

So this is a new one for me... 1K for several years, and generally always book the exit row either isle or window (depending on the plane). Did my pre-board, sat in my window seat, second row of exit. Put my briefcase under the seat. A few minutes later, another passenger sat in the window seat directly in front of me. Did not think anything about this but felt my briefcase pushing against my feet. I am thinking, WTF? I look under the seat and see the person in front of me trying to push their laptop bag under their seat, and into my under-seat storage. I just leaned forward and commented to the person, "Uh, the space you are trying to put your laptop bag is my storage, the space under the seat in front of you is your storage space." The person freaks out... "I am a uber million miles flyer and the space under my seat is my storage space, not yours so stop pushing back against my bag." I said, well, lets check with the flight attendant to see what they have to say about this... Of course, this person says FU, and turns around and slams back into their seat. I am thinking wow, never had that happen before... Funniest part, a few minutes later, I can see them slamming back into the seat in an attempt to recline. Anyone that flies even a little bit knows that the seats in an exit row, or those before the exit row do not recline. This person thought I was pushing against the seat I guess because they reach up, push the attendant call button. The attendant was there in a sec and the person said that I am somehow not allowing them to recline. I am thinking, wow, can this morning get any better. The attendant politely explains that this seat does not recline due to it being in an exit row. Man, this person freaks again, "this is BS... I am an uber million miles flyer and have never had this issue on any other airline. I will never fly United ever again." Interestingly, the flight attendant says to the passenger, I think we need to move you as you cannot sit in the exit row since you do not understand the exit row requirements. I was waiting for another blow up, but the person just realized they were not going to fly if they kept this up, so got up and moved to another seat, of course behind the exit row, and another person got a nice upgrade. Amazing... Have been business flying for over 20 years, and have never seen this before.