What about food? If you go to Italy and declare that your favourite pizza topping is pineapple, I assure you it will not be received well. If you put chorizo on paella, you would be scorned in Spain… Go to an American police station and declare that doughnuts suck, and you might get shot.
Any topic that people are passionate about, and you are going to see plenty of arguments and see some unpopular opinion pop up.