The Beard thesis that all American history can be explained by economics has been debunked. It's really nothing more that the Marxist view of history in disguise. In American history, ideas matter, as the Democrats just learned again in 2004.
You've pretty much nailed it.
Though I think some sincere folks making that argument aren't being dishonest so much as deluded - or highly selective - in their reading of history.
They really believe that states rights were destroyed by the Civil War. But they run into the problem of taking slavery off the table when they take that position. So, Presto! they look hard for - and find - economic causes for the war.
All the while overlooking what was the lynchpin of the southern economy.
I do think efforts to re-fight the Civil War or blame Lincoln for the size of the late-twentieth century Federal government serve no useful purpose.
The fact is one of the paradoxes of American history is that the United States, Reagan's shining city on a hill, arose out of a slaveholding society that nevertheless produced the Declaration of Independence and Constitution.
The Civil War is over and we are now one nation. I honor the sacrifices of the people on both sides and absolutely disagree with those today (mostly liberals) who try to tarnish the memory of those who fought for the South.
But these endless debates claiming slavery had nothing to do with the Civil War get us nowhere. You might as well ask, "other than that, Mrs. Lincoln, what did you think of the play"?