The entire point of the South seceding was to preserve slavery.

What that website is ignoring is that slavery was an integral part of southern culture and they were not willing to abandon it.

To drive this point home, read the declarations of secession for South Carolina. Very specifically written in the document is the grievance that the northern states refused to return escaped slaves against the wishes of Southern states.

The problem with the "The South was going to end slavery" argument that such an program would have required strong executive action to accomplish. Most proponents of such an argument forget that the war time experience of the CSA saw state governors thwart most attempts by the national government to utilize executive power.

We see this in Georgia's resistance to conscription and keeping their 10,000 man strong state militia from serving outside the state. We see this in North Carolina's retention of vital supplies, such as clothing, food, and arms, while Lee's army starved and subsequently surrendered at Appomattox. We also see this in slaveholder's removal or refugeeing of their slaves away to the Confederate interior, rather than have them requisitioned by the state to perform valuable military labor. Literally as the Confederacy lay dying, slaveholders continued to withhold their property from the Confederate war effort, resisted attempts to plant staple instead of cash crops, and even traded with federal government agents or Union military authorities.

In each state, a minority of slaveholding elites resisted every attempt by the CSA government to assert any type of control or authority over their slaves. In addition, these elites would have prevented any measure ending slavery from passing each state's legislature. Thus, Jefferson Davis would have been required to take such action himself, as as I have just described, such centralized actions were consistently thwarted at every turn and level.

As to your comment on the South being anti-democratic, this is complicated, but basically true. As numerous historians have shown, the South (really different and diverging "Souths" with unique characteristics, constituencies, demographics, economies, etc) contained a strong strain of anti-democratic ideals and tendencies in their politics and social structure.

To even pass secession ordinances, large scale intimidation was conducted by fire-eaters and their allies, ranging from verbal threats, to expulsions, and to outright violence. Anti-democratic violence was a staple of southern politics, preventing vast ranges of policies or even discussions from occurring. This is not only true for the secession crisis, but also took place during local elections and in the debates over the creation of territorial governments (i.e. the Lecompton Constitution and Bleeding Kansas).

In addition, violence was used to maintain the social order of the South. Any individual who discussed abolition could be threatened or killed, as could any individual that was believed to be involved in the Underground Railroad. Violence was used against women suspected of carrying on interracial relationships, as was similarly employed against slaves or freed men in similar situations. Violence also happened over religious differences in places like Virginia in the 1790s. Furthermore, leading anti-democratic proponents, such as South Carolina's elites, hated the egalitarianism and democratic tendencies of the era, and stubbornly resisted all attempts to enfranchise more of the white lower classes. South Carolina even up to 1860 was one of the few states that still resisted allowing the voters to select gubernatorial candidates. It should be said that this isn't the only strain of thought in the South or that the entire South believed in this. But it is worth stating that amongst the elites in each Southern state, there were strong anti-democratic ideals and they enthusiastically used their lower class compatriots to carry out extra-legal paramilitary coercion throughout the antebellum era. These attempts of course were resisted by numerous southerners who did believe in the democratic and egalitarian spirit of the era, but it was a constant battle between "democracy and despotism" as William W. Freehling describes.

I should also point out that in the North too did contain an anti-democratic strain as well, as we see in the violent suppression of abolitionists in the 1820s and 30, as well as the attempts to disenfranchise new immigrants in the late 1840s and 50s. However, such violence was not as widely prevalent, nor was it so publicly sanctioned in the North as it was in the South.

It is no small wonder that the Confederacy, which preached the principle of "consent of the governed" actively celebrated the fact that 2/3rds of its population were disenfranchised. And that simple fact illustrates the deep strain of anti-democratic thought within the CSA.

Sources: Daniel Walker Howe, What Hath God Wrought: The Transformation of America, 1815-1848 (2007); Richard John, Spreading the News: The American Postal System from Franklin to Morse (1995); Eric Foner, Free Soil, Free Labor, Free Men: The Ideology of the Republican Party before the Civil War (1970); Steven Hahn, A Nation under Our Feet: Black Political Struggles in the Rural South from Slavery to the Great Migration (2003); Stephanie McCurry, Confederate Reckoning: Power and Politics in the Civil War South (2010); Eric Foner, Reconstruction: America’s Unfinished Revolution, 1863-1877 [unabridged] (1988); William Freehling, The Road to Disunion, vol. 1: Secessionists at Bay, 1776-1854 (1990); William Freehling, The Road to Disunion, vol.2: Secessionists Triumphant, 1854-1861 (2007)

The CSA Constitution would have to be modified to allow slavery to be outlawed throughout the CSA just like the US Constitution required. It also promised a republican form of government.(http://avalon.law.yale.edu/19th_century/csa_csa.asp)

The CSA Constitution did have a ban on slave importation from any foreign nation or non-slaveholding states of the USA (Article I Section 9.1). It also allowed the Congress to ban importation from the USA completely (Article I Section 9.2). It also had a section regarding new states and slavery (Article IV Section 3.3) that says new states can decide to be slave or not. EDIT: /u/hatari_bwana pointed out that I had misread that part of the Constitution. Territories had to allow slavery as they were under the control of the CSA and not states. Only full states could determine on their own if slavery was legal in their boundaries. And even then each state had to allow slaves from other states to pass through without interference no matter the legality of slavery within it.

All of this being said, the Constitution itself allowed for states to ban slavery if they wanted to. It is quite possible that states would have started to ban it not long after the Civil War, but then again maybe not. I can't find any documents regarding plans to do so.

Those answers are dancing around things that are generally true, but doing a not-so-great job of presenting them.

As to the first one about democracy vs. aristocracy . . . it's generally the case that Southern plantation owners were more likely to model their culture after European aristocracy, even at a time when the rest of the nation was embracing a much more (theoretically) egalitarian approach to what it meant to be white and male in America.

So, for example, when it came to politics, in the immediate aftermath of the American Revolution, the Southern states, in general, were more likely to require higher thresholds for property-owning when it came to the right to vote and hold office than were seen in, say, Pennsylvania and New Jersey, which were much more democratic.

Likewise, as the enthusiasm for 'common man' politics and a preference for avoiding ostentatious displays of inherited privilege became more common in the early 19th century North and West, the South (particularly the wealthy South) weren't so eager to unseat traditions regarding deference to one's social betters and the respect for old money.

From all of the sources I'm familiar with, the CSA was on board with republican democracy. They just had a different political and socio-economic culture that didn't really require or champion the idea of participation from below in the way that the North and West did.

As to the second part . . . toward the very tail end of the war, when it became clear to the CSA that the war was not likely to end in their favor, there was a desperate attempt to secure support from European nations in which the proposal of abolishing slavery was brought up, as no European nation was willing to side with the South over this issue. It's not entirely clear how serious an offer this was, or that the CSA would have been able to fulfill this promise had any nation taken them up on it (Jefferson Davis may have been willing to make that promise, but it's doubtful that his supporters were).

While I know of secondary sources on the topic that treated this like a genuine offer and used it to make the argument that the Civil War wasn't really about slavery, they're all 30+ years old and not particularly well-respected. See, for example, the sources that the site you linked to use. The only times that site draws on modern scholarship, it's to cherry pick facts that are generally presented out of context to fit a particular interpretation.