You’re being disingenuous. Violence doesn’t have to be a physical threat to be considered violent. If colors, coughing, and arguments can be described as violent, hate mail most certainly can. Especially if it’s threatening someones life or livelihood.
US Department Of Justice:“The “crime” in hate crime is often a violent crime, such as assault, murder, arson, vandalism, or threats to commit such crimes. It may also cover conspiring or asking another person to commit such crimes, even if the crime was never carried out.”