It is no figure of speech.

On the Continent they do sincerely believe that every Englishman is mad.

They are as convinced of it as is every English peasant that Frenchmen live on frogs.

Even when one makes a direct personal effort to disabuse them of the impression one is not always successful.
It was a comfortable little restaurant, where they cooked well, while the Tischwein was really most passable.

We stopped there for a couple of hours, and dried ourselves and fed ourselves, and talked about the view; and just before we left an incident occurred that shows how much more stirring in this world are the influences of evil compared with those of good.
A traveller entered.