Your complaint about hasty generalization/unrepresentative sample in the poster's supposed inductive error may be hard to support.
The question in court would be called "patterns and practices", and the question here is whether 1) the Cherokee were justified in 1861 in seeing parallels to their removal 25 years before in terms of federal policy and practice, and 2) whether their resulting support of the Confederate position supports Aurelius's writer in concluding that Cherokee agreement with the Confederates that USG had indeed engaged an abusive policy toward divergent (but presumably protected) interests, and that such actions were typical of the ninteenth-century United States Government, does in fact constitute contemporary support for the Confederate position on secession and the Civil War.
It doesn't exactly make the scales go "clang", but it's interesting that the Indian nations sided with the Confederates when they could have remained neutral, and that they said that they took sides out of their own perception, that the Lincoln Administration's policies toward the South reminded them of Jackson's policies toward them, which is a pretty damn strong thing to say, given what they'd been through.
The best way to subvert the document's apparent support would be to allege undue influence by Confederate agents, or some sort of credible coercion.
Anyway, at the point I've just reached, he's declared himself a big fan of Gen. Joseph E. Johnston! I don't believe I've ever come across such a thing :-); gives me something new to hunt for in the library.
Do you have an opinion on Johnston, Stainless, or a book to recommend?