Did they singlehandedly ratify the Constitution or were they perhaps outvoted by their colleagues? Consider the ratification of New York [Link]:
Ratification of the Constitution by the State of New York; July 26, 1788.
WE the Delegates of the People of the State of New York, duly elected and Met in Convention, having maturely considered the Constitution for the United States of America, agreed to on the seventeenth day of September, in the year One thousand Seven hundred and Eighty seven, by the Convention then assembled at Philadelphia in the Common-wealth of Pennsylvania (a Copy whereof precedes these presents) and having also seriously and deliberately considered the present situation of the United States, Do declare and make known. ...
That the Powers of Government may be reassumed by the People, whensoever it shall become necessary to their Happiness; ...
... Under these impressions and declaring that the rights aforesaid cannot be abridged or violated, and that the Explanations aforesaid are consistent with the said Constitution ... We the said Delegates, in the Name and in the behalf of the People of the State of New York Do by these presents Assent to and Ratify the said Constitution.
What did they know, right? Hamilton and Jay were members of that ratification convention, and Marshall and Madison were members of the Virginia ratification convention that said something similar. If they felt otherwise, they got outvoted.
Hamilton is also on record in that NY Ratification Convention as saying:
It has been well observed, that to coerce the States is one of the maddest projects that was ever devised. A failure of compliance will never be confined to a single State. This being the case, can we suppose it wise to hazard a civil war? Suppose Massachusetts or any large State should refuse, and Congress should attempt to compel them, would not they have influence to procure assistance, especially from those States which are in the same situation as themselves? What picture does this present to our view? A complying State at war with a non-complying State; Congress marching the troops of one State into the bosom of another; this State collecting auxiliaries, and forming, perhaps, a majority against its federal head. Here is a nation at war with itself! Can any reasonable man be well disposed towards a Government which makes war and carnage the only means of supporting itself -- a Government that can exist only by the sword? Every such war must involve the innocent with the guilty. This single consideration should be sufficient to dispose every peaceable citizen against such a Government.
Not quite sure what you believe that post proved but there is not question that there is one legal way to change the Union and that is through amendment of the Constitution.
Nowhere was it claimed that rebellion was the means of changing our Union or that insurrection was justified when some people became unhappy.