Broken Communication

Over the years I have had people break off communication for what to me were odd reasons. Some of these were people I considered friends, and some of them were people I knew slightly or had just met.
There was the person I remember from when I was in a dorm. There was a girl who was a friend with my roommate. We were talking about music, she mentioned some music that she liked, but I did not enjoy. I said that I did not like it. She got angry and said she would not be friends with people who did not like music that she did. I was relieved that she stopped speaking to me. This same roommate had other friends who acted the same way.
Later when I was still in school I met someone from Toronto, Ontario, Canada. We were having a pleasant conversation. We talked together until the subject of our majors came up. When she learned that I was studying French she abruptly stopped speaking to me. Another situation where I was not to upset not to have further contact. If she was that intolerant I was better off without her.
There was someone I had thought of as a friend. We had spent a lot of time talking and sharing musical tastes. She was someone with whom I thought I could talk openly. We corresponded for awhile. She sent a letter in which she  wrote about a book with which I was well acquainted. I cannot remember what she said, but it seemed like pseudo-intellectual bullshit. I politely disagreed with what she had written. I told her what the author of the book had said. I received a very angry response in which she said that I was being a typical man in disagreeing with her. She wrote that if I wrote again she would refuse my letters unopened. I never heard from her again. If the roles had been reversed I would not have become angry, but would have been happy to get new information. I was sad to see the friendship end, but I felt that if she was willing to end a friendship over something like that it was not a true friendship.
Sometimes with self-righteous people I have asked them questions that I know will piss them off. It usually has the result that I want. They stop bothering me. Usually they are the arrogantly ignorant people I mentioned before.