Political Memes

Don't forget the Electoral College there too... They get electors based on a non-voting population

From my understanding it was much more about the refusal of free states to cooperate in returning escaped slaves than it was about taxes. I've never heard of a tax based on the population of a state.

Little more complicated (but also less complicated at the same time, somehow) than that. A lot of it also had to do with the inevitability of the United States moving away from slavery as an institution. The Missouri Compromise effectively prevented any further parts of the remaining Louisiana Purchase territories from entering the Union as slaveholding states. The Dread Scott decision overruled this in 1857, but by this point the damage was done and animosity between the two halves of the US was coming to a head. To add to this, Alexander Stephens and others very publicly called for secession on the basis of preserving slavery as an institution. See Stephens' "Cornerstone Speech" and the various declarations of secession made by the former Confederate states themselves for additional details. So, taxes were possibly a component, but the core driving motivator behind secession was in many ways more fundamentally the preservation of slavery. One could even argue that the taxation argument is a way of whitewashing what is fundamentally a motive for the preservation of slavery, as the Revolutionary War was fought on the basis of taxation without representation and the Confederacy wanted to draw explicit parallels to their secession and the United States' secession from England, however specious that comparison might be.

I think the “tipping point” so to speak was much closer though. There was the Fugitive Slave Act of 1850, which took away Northern states’ right to not be complicit in slavery. Then in 1861, Kansas entered the Union as a free state and the slavers were now out-voted in both the EC and Senate. Shortly after Kansas became a state, they attacked the US.