Bad Food Analogy:
People are less likely to comment on and remember a good meal at a restaurant than they are a bad one. After getting a bad meal, people will often avoid going to that restaurant for years, even after it’s changed management, etc, and in the meantime, they’re likely to tell all their friends that they had a bad meal there. In much this way, people still tell bad stories about the Musicians' Union that are decades old and no longer relevant. See also Myths and Rumors.