Why do parents get so upset when their children marry outside their religion or ethnic background?

Each race has their own traditions, styles of food. Religion is an issue dependent on which culture you marry into. The cultures can be as different as night and day. I can totally understand the Italian guy. Your parents are wiser than you know. It has nothing to do with him being a nice guy, Italians can be very nice people. The difference on the way they treat wives than what you are accustomed to would be horrendous for you. Study your different nationalities, their beliefs, how the culture believes the man and woman are to be in the household. You will really be surprised on how different yet the same we all are in our cultures.