Imagine that you are at a job interview. There is only one other candidate for the job, a man. You have equal qualifications and equal education; on paper, you are identical, except for gender and name.
In person, however, the differences become more obvious. You arrive on time for your interview; you are well-dressed and you answer questions clearly and clearly know what you are talking about. You are very professional and make an overall good impression. The other candidate, however, is extremely unprofessional: he shows up fifteen minutes late and, while he is not slovenly, he certainly isn’t dressed properly for an interview of this kind. He stumbles over some of his answers and, while he makes some effort, he clearly doesn’t know as much about the company’s workings as you do. The impression he makes is mediocre at best.
Shortly after his interview is over, you are informed that you have not gotten the job.
Later, you are at a restaurant with a group of female friends. You are discussing, over lunch, the unfairness and apparent sexism of what has happened to you, and some of your friends mention similar incidents. You’ve been talking in this vein for several minutes when a guy who is not sitting anywhere near you passes your table on his way back from the bathroom, and overhears part of your conversation. He then sits down at your table and starts explaining to you that what happened to you was not sexism, and gives you a patronizing list of reasons why.
Presumably, this makes you pretty angry.
When you tell PoC that they are overreacting to racism, you are being that guy. This is not your conversation to contribute to, you probably don’t have the entirety of the context, and you have no firsthand experience of the situation being described. You are walking into a discussion that is not about you and telling everyone involved that they are wrong, even though you have no way of knowing this is the case.
Respect PoC’s opinions. Don’t be that guy.