Below, I had a similar debate with this person. They attempted to get me on the defensive by turning the conversation to the 2014 murder of police officers in New York, and continually bringing it up as a way to deflect from legitimate claims. They are not interested in any kind of meaningful debate -- they are only interested in inflaming tensions through antagonistic language (e.g., "are you calmer yet?") and getting you to a point where you respond in anger.
Flag and move on.