Not so fast. Texas raised a cluster of issues, two of which you've pointed to by quoting the document in part.
Among those issues were the complaint about bad faith among the Northern States, and a conspiracy to abolish slavery w/o compensation as a major issue (given the value of slaves in Texas in 1860 was greater than that of all the improved real estate in the state put together, this was no trivial or theoretical complaint), as well as repeated failures of the Congress either to provide adequate frontier defense against incursions by Mexican bandits and Comanches, or to help defray the cost of the Ranger companies the State had raised on her own, to supply the deficit, in violation of the Constitution.
There were other complaints related to the apprehension of Wideawake agitation in Texas aimed at starting a slave revolt (after the pattern of John Brown's insurrection), arson, and other maladies the Texans accused Republicans of fomenting (rightly or wrongly, but they weren't getting any satisfaction from the federal government), and various other complaints.
"It was all about slavery" is a Marxist slogan. Their analysis is actually not so much based on Marxist theories about the value of labor, as it is a tactical offensive against Republican and conservative resistance to the Marxist takeover of the federal government.
The South today is the cradle of resistance to socialism, as it has been since the New Deal. The agitation of racial issues has been the Marxist counter, from the Civil Rights Movement to today's bloody-shirt "cracker" invective and pious posturing against Confederate symbols, all of which is cynically instrumental politicking aimed at splitting off moderate conservatives in "battleground" states like Ohio, from conservative candidates in the GOP, and at inducing RiNO/RNC panjandrums to attack and marginalize conservatives within the GOP. The Marxists' aim is to prosper the soft, "Me-Too" Republicans the rolling and mugging of whom has been liberals' and Progressives' stock in trade above 60 years now, at the expense of real conservatives who will defend the United States, capitalism, and American history.
To say that Southerners, whether FReepers or not, are secretly Kluxerphiles bent on reintroducing chattel slavery is a libel and a canard, and it's been retailed here on FR for years by Marxist trolls like Non-Sequitur, justshutupandtakeit, and other hard-line "conservative-busters".
Go ahead and take their line if you want to: but I'm telling you what it is, and why it was propagated here, and in popular historiography by the "Red diaper" historians whom Bill Clinton commissioned to rewrite the American history presented to the public by the National Park Service at our military parks, to introduce this Marxist, inculpatory blame-game meme.
BRAVO!
Well said LG! Well said indeed!