But I am not going to accept the idea that the Englishman didn't know and said so in his brief usual way.

It's equally possible that he did know.

Then, you naturally ask, why in the name of common civility did he give such an answer to the American?
I believe that I can tell you.

He didn't know that my friend was an American, he thought he was an Englishman who had broken the rules of the game.

We do have some rules here in America, only we have not nearly so many, they're much more stretchable, and it's not all of us who have learned them.