If you read about the history of Zionism, you'll find most of the early Zionists were astonishingly bigoted about Arab Jews, and many of the atheist and agnostic Zionists were as bigoted about all religious Jews. Zionists were generally an arrogant lot—it's hard to set up an ethnostate if you're not. Whether it's fair to call cultural prejudice racism, we could debate, but I certainly understand using the word in its broadest sense.