Kissmequick
loony
I can't speak for Extollager, but in my house you could say that someone did something foolish, but not that someone was a "fool." After a lot of education and some of it in counseling I now believe that it was a folksy way of saying that in an argument you criticized the behavior not the person.
I can see that, I just have visions of:
Gandalf: "Fly, you fools, fly!"
Gandalf's Mum: "Wash your mouth out with soap young man!"
Like I say, there's a big cultural gap here. UK and US, two countries divided by a single language...(and even within cultures there's big differences too. Plenty over here are brought up not to swear. It's not better or worse, just, well, different.) Possibly in this instance because that 'You fool' over here usually means 'this once you have been a numpty' not 'you are a person with all the brains of a weasel's wedding tackle'. It's usually about the behaviour (a shorter version of you have been foolish today) not the person in general