This has happened to me as both the downgraded and also someone in F giving up their seat to let my wife join me! That was a crazy one.
If I tried to downgrade and someone made the kind of fuss some of you are suggesting I would just drop it and take my F seat or give it to my wife\companion. So in that case nobody complaining would win.
I thought I got petty about upgrades sometimes but seriously...someone showing someone else some love, get over it!