Amazing. People are so rude.
I've never had exactly that happen, but I did recently have a passenger in row 3 (the F bulkhead) insist on putting two bags under her seat. I asked her politely to move them (I travel with a rollaboard and a laptop-sized messenger bag, the latter always under the seat in front of me), she gave me a .....y response, and so I simply kicked them back under her feet, at which point the FA noticed and made her put them in the overhead. 5 minutes of whining ensued - "but then someone might steal my purse!".
Perhaps people should have to agree to certain etiquette terms and conditions at purchase or check-in?