I think you are missing the point.
Nazi Germany was by no means a vegetarian country. I think a better question to ask would be - could the Holocaust have happened in the mostly-vegetarian India?
Millions of people were murdered under the pretense that these people are pigs or rats. But what if your culture (e.g. Hinduism or whatever) also condemns the killing of pigs and rats? The entire argument that justifies murdering these people breaks down.