Differences of opinion are not errors.
but his errors on the Morrill Tariff, his opinions on what caused the war
Those, as I said, have little to do with the political right to secession or nullification. You will note that at the time of the WBTS, rights did not require justification, but were endowed on men by God. To suggest that the reason one chooses to excersize a right somehow weighs on the existence of such is to deny that right based on your interpretation of events. The article's focus is not the tarrif or the reason for secession, but a call for our state leadership to grow some hairy clankers and push back against Leviathan for once.
and what it should be named,
Matter of opinion. I certainly would not call it a 'civil war' just because there was not fight over control of Washington and the government of the US. If you choose to call it a rebellion, then I cannot generate a coherent argument against that, but you and I both know that a rebellion is not necessarily a 'civil war' unless your definition of the latter is broad enough to include all domestic disturbance.
reason why the southe seceded,
See above. This has oft been a point of contention on these threads. Had the North fought the war to end slavery, then you would likely hear no argument from me and many others. Unfortnately, the end of slavery was incidental to war that was waged for a stated different purpose, yet there are those who demand we pay homage to Lincoln for ending slavery when it was not his stated goal. It is like praising Stalin for the effectiveness of today's US military.
Merriam Webster defines civil war as "a war between opposing groups of citizens of the same country." That description would certainly fit.
Had the North fought the war to end slavery, then you would likely hear no argument from me and many others.
But my contention was with Dr. Williams' explanation for why the south seceded. Defense of the institution of slavery was the primary reason for the southern rebellion yet it is treated as the crazy aunt in the attic by all you sothron supporters, as if by refusing the acknowledge it will make it go away. Dr. Williams refuses to admit it and that, as much as anything else, makes all his opinions suspect. IMHO, of course.