This changed?
The Due Process clause just states that the government has to follow the law when depriving you of freedom or property. If the law says that the process is to stuff you into a circus cannon and shoot you into the ocean then you are guaranteed that.
Who told you this information? Immigration violations are still supposed to be heard by a court and fair representation is required.
Multiple immigration lawyers. The fact that there is no judicial review and the CBP officer at the port of entry is empowered to deport you immediately and ban you from entry is quite important and I am sure you'd been advised just as well if you had hired a semi-decent immigration lawyer too.