They choose their profession and are aware of the dangers that they face. They also already have special laws that mandate heavier sentences for crimes committed against police officers than of regular citizens. Hate crime is a designation for either people who are hated for something circumstantial that they can not help like race, gender, nationality, gender-identity (homosexuality) or religion which is supposed to be a benign choice that doesn't impose or infringe on anyone else (because in the US, we have freedom of religion and a separation of Church and State).