Answer:Demon has to do with evil and everyone outside Tang community did evil things that were very unpleasant to this community and because of these actions that were done to them.
Laurence Yep refers to them as demons because they did not allow Chinese people to bring their families over to the United States and some of their community members were exposed to harsh treatment such as being beaten up by these people he referred to as "demons"
Explanation: This is a negative connotation it evokes negative feelings towards whomever is called a demon. It evokes a feeling of these people being considered very evil.