You're right, anger against the north had been brewing since before the 1860s. The government passed the Tariff of 1828, which increased the cost of foreign products to encourage manufacturing in the north. It was the highest tariff in the nation's history. The south sold cotton to Europe and bought items in return, but this tariff made these goods the farmers needed too expensive. Also, the Constitution does not ban secession, not mentioning it as a power denied to the states in Article 1, Section 10. The Declaration of Independance even supports the right to secede, stating "whenever any form of government becomes destructive to these ends, it is the right of the people to alter or abolish it." The northern states illegally invaded the Southern states to force them to remain under their government, which is tyranny by any definition.
The "Tariff of Abominations" provoked the South Carolina nullifiers to threaten secession until Andy Jackson threatened to hang them. Then some of the rates were reduced but the point is that these tariffs were voted in when the South had majorities in the House and Senate. Those tariffs affected the farmers of the West and North just as negatively as those of the South but the North had the initiative to build industries under their protection which, except for Virginia, was never done. Slavery prevented the South from modernizing and putting its capital into industry. No foresight killed any chance of success in the modern world.
There was no invasion by the North of a legitimate country.
By trying to destroy the Constitution the RAT Rebels forced Lincoln to abide by his oath and preserve and protect the Constitution.
It is a falsehood that there was ever a right to secede from the Union had there been it would have been spelled out as to how to do it. Nor would we have had a real constitution if there had been such a right. If you don't believe me just ask James Madison who proclaimed once in the Union always in the Union.
The only legal way to split the Union is through Constitutional amendment which was never tried. According to the Southern argument there was no such thing as a Constitution just a sort of list of suggestions. The DoI does not apply to this case since the means of changing the government was provided to the people within the Constitution. Nor was there any "tyranny" threatening the South prior to the War the only tyranny there was that run by the Slavers.
Protecting the Union and Constitution was not "tyranny" either since the latter clearly spells out the power to put done insurrections and rebellions.
There are no valid arguments to support the traitors who carried out the RAT Rebellion. Not one.