A weird explanation of the Holocaust

By a Russian man, in his early fifties, born in Russia, arrived in USA when he was 26.
His second wife is Russian too and got converted in the last three years.
He asked me questions like a rabbi: why do i feel, my Jewish relatives, blood, what i knew about Judaism… To become or to be Jewish is not only to be but to practice, to follow the Jewish rules… according to him. To become a Jew is a lot of work, i agree. I am working on that, slowly, to understand who i am and where i am going.
He said that he forgot G-d at a moment in his life, and he was into trouble, and punished.
"If i am your father and you are my daughter. If you forget about me, i will forget about you. That's the same with G-d. It's written in the Torah. If you forget G-d, you will be punished."
Then, his explanation of the Shoah. "The Jews in Germany forgot about G-d, sent their children to public school… And G-d said in the Torah: "For one man killed, ten should die. For one hundred, one thousand…". G-d punished them not to listen to Him."
He gave me cold sweats: "Do you think that Jews deserved a punishment like the Holocaust?"
"Yes, he replied. They sinned. That's in the Torah!"
I stopped saying something, i didn't even try to argue. I can't hear that, sorry! I let him in his delirium tremens.
Then he went back with his wife. She bought non Kosher food for him! Put in order your own house!