It is axiomatic that the present we now know inevitably followed from the history that preceded it. When you look at the U.S. federal government that now exists, it must have assumed its current form either by design of the Constitution, or contrary to that design. In case of the latter, the Constitution was entirely unable to prevent the government that it established from evolving into a form contrary to its design. Maybe the process was slowed somewhat. We cannot know for certain.
Therefore, if you dislike the current form of US federal government, it is nonsensical to idolize the Constitution, or any other causally-related fact of history. History gave us the present. If you do not like the present, and wish the future to be different, do not repeat the mistakes of the past. Whether history could have given us another present is irrelevant, because it did not.
In the end, whenever a living human fights with a document, the human will emerge victorious, and the document will become confetti. The Constitution is nothing without a living human to be its champion.
Spooner was criticizing the actual form of our current Constitution. GP was making an appeal to the Constitution and the judicial system's ignoring of it. I agree with Spooner that a Constitution such as ours is completely powerless to prevent individual judges from rewriting every time it fits their fancy.
We've basically had an ongoing Constitutional Convention in the federal courts since the founding -- without the consent of the people.