All that is necessary for the triumph of evil is that good men should do nothing[1].  To wit[2]:

When they came for the communists,
I did not speak out;
As I was not a communist. 

When they locked up the social democrats,
I did not speak out;
I was not a social democrat. 

When they came for the trade unionists,
I did not speak out;
As I was not a trade unionist. 

When they came for the Jews,
I did not speak out;
As I was not a Jew. 

Then they came for me,
And there was no one left to speak for me.

[1] Uncertain attribution.

[2] Martin Niemöller (1892 – 1984). There are several versions of this poem as Niemöller said it different ways at different times (1946 – 1984).  He described this version as his favorite.