And the question I... “mustache”... is, “Why?” (I'm so sorry.)
But it doesn't come across as realistic, so it's not quite a bad book. It's clearly trying to be silly. It's almost like it's a parody, without really having a clear reference point of what it's a parody of. But I'm not sure prejudice is a topic to be silly about.
Message
It's like they're saying that it's okay to discriminate against people with certain mustaches, because your mustache will change to fit your personality.