At no time did I allege a private party denied OP due process, but in order for a court to enter a judgment, it must first acquire jurisdiction over the person or property depending on the type of case.
In doing so it requires the plaintiff to have the deputy clerk sign a summons and have it served. This is an official communication from a governmental branch notifying you that a suit has been instituted against you and provides you notice as required by Due Process. It also advises you of the hearing and of your right to be heard at that hearing.
This is required of the court to obtain and exercise jurisdiction; this has nothing to do with a private party.
Now had I alleged a private entity had denied him due process and that were the claim, you would be correct. However we are talking about court process through a governmental branch, as such in my humble opinion, due process most certainly applies.
Again this is not legal advice consult counsel in your jurisdiction.