I'm joking that my friend's boyfriend's major is worthless and required very little work
Don't you think that's kind of mean?
I'm just joking around and am not spiteful.
I understand that you're only kidding. However, you need to take into account how what you say makes others feel too. That's why making negative comments about people is usually bad, since it makes them feel down about themselves.
I don't care if he feels bad.
How would you feel if someone made negative comments about you? You better focus on yourself rather than criticizing people.