"Ignoring the hatred and normalising it is how it starts.
"Hate starts small, but so does hope."
Devoy told those gathered remembrance was important, as "to cherish and protect our humanity, we must never forget our inhumanity".
Wellington mayor Justin Lester also spoke at the service, saying "we need to advance the causes of peace, of justice, and of human rights around the world".
Lester said people must not follow the politics asking them to turn their backs on "fellow humans".
"It's not enough to say that we were just following orders of that we were just trying to look the other way. All of us have a moral responsibility to be brave and to stand up to hate," he said.
German ambassador Gerhard Thiedemann said the Holocaust was "a tragedy for all of humankind".
"The view into the dark past in which Nazi Germany committed incredible crimes should sharpen our eyes for the future," he said.
"It must be our long-lasting endeavour to be engaged for peace, justice, and reconciliation."