Why do dogs always bark at people in "ragged clothes"? Is it really too poor and rich?

Netizen asks: Hello teacher, I have three dogs, one golden retriever, one border shepherd and one teddy. In fact, they are usually very well-behaved and there is nothing wrong with them. There is just one question that makes me curious to ask. I go out to walk them at 6 o'clock every morning, and sometimes I encounter an embarrassment.

The three of them will bark at them every time they see the sanitation workers far away on the road. I have to stop them a few times before stopping. Later, I complained about this in our group of dog friends, and discovered that this situation is not unique to my dog, many dog ​​owners have this experience. And not only for sanitation workers, it seems that as long as they wear ragged clothes, dogs will bark at them. Everyone thinks this is a dog's instinct to dislike the poor and love the rich. I want to ask the teacher, is this really the case?

If we look at it from a phenomenon, there are indeed a lot of dogs who will bark in strangely dressed or ragged clothes, even sanitation workers, takeaways, water delivery workers, etc. behavior. But this is just appeara