Which historical event is referenced in the poem below? Why do you think that? 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.

Poem by Martin Niemöller (1892–1984), a prominent Protestant pastor who emerged as an outspoken public foe of Adolf Hitler and spent the last seven years of Nazi rule in concentration camps.

the poetic form of a post-war confessional prose by the German Lutheran pastor Martin Niemöller (1892–1984). It is about the cowardice of German intellectuals and certain clergy—including, by his own admission, Niemöller himself—following the Nazis' rise to power and subsequent incremental purging of their chosen targets, group after group. Many variations and adaptations in the spirit of the original have been published in the English language. It deals with themes of persecution, guilt, repentance, and personal responsibility.

Explanation:

wikipedia

freedom of speech is also protected by the 1 amendment.

explanation:

here is pretty much what the 1st amendment says:

congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof; or abridging the freedom of speech, or of the press; or the right of the people peaceably to assemble, and to petition the government for a redress of grievances.