Holocaust survivor Dr. Henry Oster watched in disgust from his Woodland Hills home as hate reared its head during a deadly rally earlier this month in Charlottesville, Va.

The images of neo-Nazis and white supremacists brought the retired optometrist back to his childhood in Cologne, Germany, where he witnessed Nazi party members marching and chanting anti-Jewish slogans.

After years of laws and policies targeting Jews, the young Oster and his parents were forced by Nazis into the Lodz Ghetto in Poland in 1941. His father, Hans, died of malnutrition and exhaustion after several months of hard labor. His mother, Elisabeth, was ultimately killed in the gas chambers at Auschwitz.

Oster, who survived four concentration camps, was liberated in the Buchenwald concentration camp by Gen. George S. Patton Jr.’s 3rd Army. He was 16.

His story is told in the 2014 memoir “The Kindness of the Hangman,” which Oster co-wrote with his patient Dexter Ford.

We sat down with Oster, 88, to ask his thoughts on recent events. Here are excerpts, edited for clarity:

Q: What went through your mind when you saw the images in Charlottesville of white supremacists and the neo-Nazis?

A: Well of course, seeing the images of Charlottesville was a dramatic reminder of having seen exactly the same thing in the 1930s, especially around 1935 when I was 7 years old because that was the manner in which the Nazis tried to create confidence in the general population and to create trust by seeing the force and the militarism of demonstrations.

The flares and the lights and the marches were the way that they could indoctrinate the general population of most cities, except the Germans had all been wearing (brown-shirt) uniforms. … The makeup, the composition of the participants was eerily the same. These were the down and outers … the nonachievers, the incompetent, and mentally — shall we say — restricted or limited, who found certain satisfaction of being picked up and (becoming) part of any kind of a group.

Why not let (neo-Nazis) march if we believe in the First Amendment rights to free speech, expression and freedom to march? I believe they should march simply on empty streets, and as far as I’m concerned, like some countries do … we do not (do) anything different than what we (do) simply for a marathon, block off the accessible streets by barriers and let them march and let them yell into the air. They won’t have anybody to talk to, to convince, let them out for the hell of it. … I believe the Nazi Party and any other organization has the right to demonstrate and to exist. It’s our job to curtail them, to control them, but not necessarily to obliterate them.

On hate groups

I had certain reservations about our past (U.S.) history as anti-Semitic as it was, not allowing refugees to come in during the war or before WWII. [They] had a huge demonstration in Madison Square Garden [in 1939] supporting the Nazi party, which was well-established in the U.S., known as a political entity.

If you had 30,000 people show up supporting the then-Nazi party, which was legal in the U.S., you wonder how much of a remnant there is in our American psyche to support extremism of this kind. So there is no surprise that you have isolated groups re-establish themselves, growing in numbers if it promises something that people in need or in ignorance feel appealing.

I was very surprised when a national poll showed that in California we have 79 (active) hate groups known to our government. … I did not expect that underground groups, which now have become more visible with our president’s encouragement or at least permissiveness, I did not expect to have that many groups because they are not necessarily visible or known to us.

Q: How do you feel about that?

A: First of all, I don’t — surprisingly — feel threatened. I’m annoyed. I’m angry. Disappointed but not threatened. I believe this country, I see it as a leaking ship, a big ship with leaks. Sometimes it leans to the left. Sometimes it leans to the right. But I have confidence that the country … knows how to plug the leaks and to right the ship sooner or later. In the meantime, we have a lot of plugging to do.

Q: On going back to Germany in 2011 for the first time:

A: In 1941, 2,011 Jews from Cologne were deported to Lodz in Poland. In 2011, having swore never ever to set foot on German soil, the city of Cologne contacted us, or more or less discovered me. They didn’t know I had survived … and they invited us to come.

We had a big decision to make, having vowed never to return to Germany and kept it for 70 years. We decided that I will go because of the 2,011, only 23 survived the war, and in (the year) 2011 and since then, I’m the only one left, so we decided to go.

When people ask me, “Henry, after all these years, what’s the one reason that made you go?” I usually flip my [middle] finger. … [It’s] defiance and to show [the Nazis] that after all these years, now over 75 years since 1941, the attempt to kill 2,011 still hasn’t succeeded.