THIS. Also, to prevent people from misquoting this poem in the future, here's the whole thing, written by German Lutheran pastor Martin Niemoller in 1946:
"First 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 for me."
What's more Niemoller was a national conservative. He originally supported the Nazi Party, hoping it would bring about a national revival (as did many Germans), until Hitler proclaimed the supremacy of state over religion and Protestant churches, at which point he allied with other pastors and Lutheran organizations against Nazification. He was also anti-Semitic, making many pejorative remarks about Jews, such as them deserving persecution for crucifying Jesus and believing they should be kept out of any positions in the government. He was imprisoned from 1937-1945, during which time he reconsidered his earlier views.
This poem is a warning, not because Niemoller saw it happen. It is because this is his story. This poem is him saying "don't be how I was, because for however much you support a regime and the hate it doles onto the people marginalized and labelled for extermination, they will one day come for you, like they came for me". No one is immune from the prejudice of the state - there is never only one scapegoat.