All men over 40 are scoundrels

Yes. The quotation occurs in the “STRAY SAYINGS” subsection of Shaw’s Maxims for Revolutionists. The immediate context is particularly revealing because Shaw surrounds the famous line with remarks about progress, decadence, reformers, youth, and age.

Here is the surrounding passage, with the central line in bold:

“Decadence can find agents only when it wears the mask of progress.

“In moments of progress the noble succeed, because things are going their way: in moments of decadence the base succeed for the same reason: hence the world is never without the exhilaration of contemporary success.

“The reformer for whom the world is not good enough finds himself shoulder to shoulder with him that is not good enough for the world.

“Every man over forty is a scoundrel.

“Youth, which is forgiven everything, forgives itself nothing: age, which forgives itself everything, is forgiven nothing.

“When we learn to sing that Britons never will be masters we shall make an end of slavery.

“Do not mistake your objection to defeat for an objection to fighting, your objection to being a slave for an objection to slavery, your objection to not being as rich as your neighbor for an objection to poverty. The cowardly, the insubordinate, and the envious share your objections.”

And it continues immediately afterward:

“Take care to get what you like or you will be forced to like what you get. Where there is no ventilation fresh air is declared unwholesome. Where there is no religion hypocrisy becomes good taste. Where there is no knowledge ignorance calls itself science.

“If the wicked flourish and the fittest survive, Nature must be the God of rascals.

“If history repeats itself, and the unexpected always happens, how incapable must Man be of learning from experience!”

One important point

This makes the “over forty” quotation more interesting than the isolated quotation suggests. It is not simply a joke about old men. Shaw has just been talking about decadence and the reformer who becomes aligned with the very people he opposes. Then he says:

“Every man over forty is a scoundrel.”

Immediately afterward he contrasts youth with age:

“Youth, which is forgiven everything, forgives itself nothing: age, which forgives itself everything, is forgiven nothing.”

So there is a deliberate sequence: progress → decadence → reformer → forty → youth/age → slavery → resistance to defeat.

Interestingly, an early commentary on Shaw records that the critic actually asked Shaw what the “over forty” aphorism meant. Shaw’s reported explanation was essentially that a man over forty had already performed most of his useful function and was therefore becoming, “in a manner, a parasite.”

That explanation is important if you’re interested in what Shaw actually meant rather than the modern meme-like interpretation of the quotation.