Remember, the point of this discussion is DiogenesLamp's hope to equate the terms "United States" and "United Kingdom" as being equivalent "Unions".
Then, having posited that the British Empire was really just a "Union", like the USA, he claims that secession from the American Union was just as legitimate as secession & rebellion against the British "Union".
Actually, he wishes us to believe that rebellion against the Brits was illegitimate, while secession from the United States was totally A-OK.
In other words: if it was OK for our Founders to "secede" from the British Union, then it must be much more OK for Confederates to secede from the American Union, right?
The problem is, those two histories are in no way legitimately comparable, unless we give Confederates the role of 1776 Brits!
For starters, in 1860 there was nothing remotely resembling the "long train of abuses and usurpations" listed by our 1776 Founders.
Further, the British Empire "Union" was established and maintained by military force -- nobody volunteered to join and nobody could leave except by rebellion.
The American Union was much different -- joined together by mutual consent, it could be dissolved by mutual consent.
Indeed, Civil War only came in 1861 because Confederates provoked, started, declared & waged it, primarily in Union states, for the first 12 months.