How to refute that mountain pigs can't eat fine bran

You can refute it in the following ways:

1, don't use stereotypes to evaluate people: it's not that wild boars can't eat fine bran, but they may not have a chance to eat it. Similarly, a person may not be exposed to some good things, but it doesn't mean that he can't appreciate or cherish them.

2. Give people opportunities to learn and grow: People can expand their horizons and tastes through learning and experience. If a person has never been exposed to good things, you can give them a chance to try and understand.

3. Tell the truth: If you think a person has never seen the world, you can change his opinion by exposing him to more beautiful things. At the same time, if you think a person knows how to appreciate beautiful things, you can prove your point with facts.