People often repeat this poem/quote:

First they came for the Communists
And I did not speak out
Because I was not a Communist

Then they came for the Socialists
And I did not speak out
Because I was not a Socialist

Then they came for the trade unionists
And I did not speak out
Because I was not a trade unionist

Then they came for the Jews
And I did not speak out
Because I was not a Jew

Then they came for me
And there was no one left
To speak out for me

And they enthusiastically agree and vow not to repeat the same mistakes. However, the quote has another, often overlooked dimension: the author was a conservative priest who initially supported Hitler on his rise to power. This guy hated communists with burning passion and didn't particularly care for Jews, either. Nevertheless, he later came to bitterly regret not speaking out for these godless troublemakers. That's the important message.

People see it and think "Oh, yeah, I will stand for nurses even though I am not a nurse, I will stand for black people even though I am not black!" But then "they" come for sex offenders, or Jehova's Witnesses, or illegal immigrants, or other group that "had it coming". And no one will speak out.