For the lazy, the quote is this:
All that is necessary for the triumph of evil is that good men do nothing. — and Burke didn't say it. (Did Burke say anything in 15 words?) Apparently we have JFK to blame for everyone thinking he did:
https://quoteinvestigator.com/2010/12/04/good-men-do/.
I love these sequences. The basic quote is known to have been said by Reverend Charles F. Aked (yup) in a sermon against alcohol (yes) in 1916. Then in 1920, Sir R. Murray Hyslop (that's right) attributed it to Burke. That clearly clicked, because we're all still repeating it.
Burke did say this in 1770:
No man, who is not inflamed by vain-glory into enthusiasm, can flatter himself that his single, unsupported, desultory, unsystematic endeavours are of power to defeat the subtle designs and united Cabals of ambitious citizens. When bad men combine, the good must associate; else they will fall, one by one, an unpitied sacrifice in a contemptible struggle.
WTF? But then John Stuart Mill said this in 1867:
Bad men need nothing more to compass their ends, than that good men should look on and do nothing.
Come on, that's obviously the quote. But how did it get from Mill to Reverend Aked? Surely not directly, because this is the passage from his sermon:
“The people in the liquor traffic,” said the speaker, “simply want us to do nothing. That’s all the devil wants of the son of God—to be let alone. That is all that the criminal wants of the law—to be let alone. The sin of doing nothing is the deadliest of all the seven sins. It has been said that for evil men to accomplish their purpose it is only necessary that good men should do nothing.”
... and in my experience that sort of preacher doesn't read Mill.
But why did Sir Murray say it was Burke? It turns out he was a temperance crusader too—but also an Englishman. I bet he stuck it to Burke because he couldn't bear to cite the American Reverend.
(I took all this from https://quoteinvestigator.com/2010/12/04/good-men-do/, which is the same URL I mentioned earlier.)