Due process is what is due to the accused in a criminal trial. If, e.g., murder was legal then there would be no accused, no trial, and no occasion for due process. Constitutional protections protect us from the government, not each other.
That makes no sense. And it is factually wrong. Ever heard of Eminent Domain? A noncriminal, an ordinary *person* under the law, cannot be deprived of property without just compensation. Same principle, noncriminal context.
The Constitution creates a system, an interlocking handshake relationship between the federal and the states, whereby the powers and limitations of the federal are intentionally shaped to the contour of natural rights, precisely because it is those rights that the system, as a whole, must defend by procedures enacted in the states. The states are no more free to ignore murder than they are to ignore slavery. And, as if to make clear what should be obvious to any reasonable person, the 14th Amendment confirms that the states can be held to a legal obligation to provide due process to all *persons* with respect to life, freedom, and property.
And really, how else can it be? There is no more basic function of government than the protection of innocent human life. Any government or any system of related governments that fails to do so is, under natural law, invalid, of no force and effect, not a real government. Why do you suppose those natural, inalienable rights were thus identified in the Declaration? For show? For pomp and high sounding rhetoric with no meaning, with no practical effect in law? Such a thought is offensive to the depth of wisdom and character of our Founders. They could not have imagined the nightmare interpretation you artificially impose on their design, where genocide, the mass murder of millions of babies, is an acceptable byproduct, as long as the states have free choice on the matter.