There are a whole set of deceitful responses that are designed to deflect the conversation away from anything useful. The "not all" argument is always dishonest. It's designed to undermine your point. I just respond with, "If there were good people, then we wouldn't have all these problems." That briefly shuts people up, and I say this as a white person. I think it's way more productive to see how criticisms do apply to you rather than deny them. Thanks for writing.