Why do people always regard their low quality as humor?

Everyone's living environment and education lead to different values. Different values will have different views when they meet one thing, that is, different people have different views. There are always people who regard vulgarity as humor, which means that at least some of their values think this so-called humor is not vulgar, or he thinks it is not worth mentioning at all. If this person is a basin friend, you can express it to him euphemistically. If it's just a general relationship, it goes without saying. Maybe he thinks there is something wrong with your values.