Bertie and his Aunt Dahlia are fans of Nero Wolfe

In 1965 Rex Stout published The Doorbell Rang. From the blurb:

There’s no one and nothing the great detective Nero Wolfe wouldn’t take on if the price was right. That’s something wealthy society widow Rachel Bruner is counting on when she writes him a check for a whopping hundred grand. But even Wolfe has a moment’s doubt when he finds out why the prize is so generous. For the oversize genius and his able assistant Archie Goodwin are about to lock horns with the FBI—and those highly trained G-men have a way with threats, tails, and bugs that could give even sedentary sleuth Nero Wolfe a run for his money.

The rich society widow read a book criticizing the bullying and backroom deal making of the FBI (some things don't change), purchased 10,000 copies and mailed them to leading businessmen, politicians, academics and leaders across the nation. Now the FBI has her under surveillance and she wants Nero Wolfe to take care of it.

Ordinarily that would have touched him, her rattling off their names like that, but not then. "I wouldn't ask them to take the risk," he said. "I wouldn't expect Mr. Goodwin to take it. Anyway, it would be futile and fatuous. You say 'stop him.' You mean, I take it, compel the FBI to stop annoying you?"
"Yes."
"How?"
"I don't know."
"Nor do I." He shook his head. "No, madam. You invited it, and you have it. I don't say that I disapprove of your sending the books, but I agree with the lawyers that it was quixotic. The don endured afflictions; so must you. They won't keep it up forever, and, as you say, you're not a congressman or a drudge with a job to lose. But don't send any more books."

Perhaps it is an illustration of my ignorance but I suspect it is an example of cultural flotsam. "The don endured afflictions; so must you."

That is almost certainly an allusion to something. Possibly it might be to Don Quixote. But that seems mighty obscure. Rex Stout lived north of New York City, was this possibly something to do with some Mafia Don cause celebre? No idea. It is an allusion tossed out in the course of a action mystery novel by an immensely successful popular writer in a book fifty and more years ago. What it was an allusion to, whether anyone caught it at the time, and how one might uncover its meaning today seems likely to have slipped beyond the realm of reasonable.

Googling various queries turns up nothing.

Well, not nothing. It doesn't get me an answer but it does get me to something I had forgotten - a connection between two of my favorite authors. From Wikipedia.

Stout was a longtime friend of British humorist P. G. Wodehouse, writer of the Jeeves novels and short stories. Each was a fan of the other's work, and parallels are evident between their characters and techniques. Wodehouse contributed the foreword to Rex Stout: A Biography, John McAleer's Edgar Award-winning 1977 biography of the author (reissued in 2002 as Rex Stout: A Majesty's Life). Wodehouse also mentions Rex Stout in several of his Jeeves books, as both Bertie and his Aunt Dahlia are fans.