You need to read up on the details of City of Castle Rock v. Gonzales.
Law enforcement officers are employed and paid to enforce the law and preserve public order. That is exactly what they do.
According to the Supreme Court, law enforcement does not have a constitutional duty to accord a single citizen special consideration. The court said that a lower court protection order does not create a property right to such special protection.
Castle Rock was an ugly decision, no question about it, and the court has come under a lot of very justifiable fire for it.
However, the easy remedy lies with the states. They can enact laws defining the duties of officers sworn, certified, or licensed in the state to address the issues raised by the Castle Rock decision.
In fact, the federal government may not even be able to legislate such laws other than those governing the conduct of federal officers. Law enforcement within a state is the exclusive province of the state itself; it's a part of the state's sovereignty.