It's rude to insult the things a person cares about.
Jim's friend loves a TV show that Jim hates, and they ask Jim what he thinks of the show.
Jim wants to answer his friend.
Jim says that he's not a fan of the show but that everybody has different tastes in entertainment.
Jim tells his friend that the show is pretty dumb and that even children would find it laughable.
Jim's friend is glad that even though he doesn't like the show he doesn't judge them for liking it.
Jim's friend is offended at what Jim thinks of something they like and their taste in general.