They often have the lowest training standards in the profession

Law enforcement isn’t a “profession.” Practitioners of real “professions,” such as medicine, law, and engineering, have “professed an oath” (that’s where the word comes from) to act in the public interest (i.e. to protect the public) and abide by a code of ethics. That includes things like acting against their own interests and refusing orders from people with power over them, if necessary. In contrast, the courts have ruled in Warren v. District of Columbia that law enforcement officers explicitly have no such obligation.