. . . muttered the ogre

Tibor Machan misreads the Declaration of Independence:

It requires “a long train of abuses and usurpations,” which reduce a government to “absolute despotism,” before secession is justified.

On the contrary, the sentence containing that phrase states a sufficient condition. The necessary condition is stated in a more famous sentence:

We hold these Truths to be self-evident, . . . that whenever any Form of Government becomes destructive of these Ends, it is the Right of the People to alter or to abolish it . . . . Prudence, indeed, will dictate that Governments long established should not be changed for light and transient Causes . . . . But when a long Train of Abuses and Usurpations, pursuing invariably the same Object, evinces a Design to reduce them under absolute Despotism, it is their Right, it is their Duty, to throw off such Government, and to provide new Guards for their future Security.

In other words:
Secession is legitimized by any state act that tends to weaken, rather than defend, the rights of the people. A revolt over trifles is not illegitimate, but it is unwise; better the devil you know. Yet the conditions complained of were so severe, so far beyond “light and transient”, as to make secession not only legitimate but mandatory.