In "The Quick One" by G. K. Chesterton, the author was describing a man, saying:
John Raggley was generally regarded as a crank. He was the sort of man who writes letters to the newspaper, which generally do not appear in the newspaper; but which do appear afterwards as pamphlets, printed (or misprinted) at his own expense; and circulated to a hundred waste-paper baskets. He had quarrelled alike with the Tory squires and the Radical County Councils; he hated Jews; and he distrusted nearly everything that is sold in shops, or even in hotels. But there was a backing of facts behind his fads; he knew the county in every corner and curious detail; and he was a sharp observer. Even the manager, a Mr Wills, had a shadowy respect for Mr Raggley, having a nose for the sort of lunacy allowed in the gentry; not indeed the prostrate reverence which he had for the jovial magnificence of Mr Jukes, who was really good for trade, but a least a disposition to avoid quarrelling with the old grumbler, partly perhaps out of fear of the old grumbler’s tongue.
I found that "have a nose for" mean "have a natural ability to find or discover"
So It may be reworded as "because he is good at finding the sort of allowed foolishness in the gentry"
But I still can't get the whole meaning that the author meant!