I don't know enough about the causes of the Civil War to comment effectively. I do know that slavery wasn't the lone or sole cause. It played a part... but there were other parts. So I don't think it is accurate to say that "otherwise good men who let their passion for the institution of slavery override their common sense."
I can understand your position. As a young man I felt much the same way as many here, that slavery wasn't "the" issue. However, after having the opportunity to work in the field of history and being able to view thousands of primary documents from Government records to personal letters, I now can only come to the conclusion that slavery was the primary catalyst that vaulted the country into the Civil War.
That doesn't infer that everyone in the South loved slavery or everyone in the north hated it. What it means is that the politically influential forces on both sides were primarily seperated by this one issue. In the years before the war, the most politically charged issue wasn't the tariffs on cotton....it was the issue of slave versus free states.
The articles of Secession for the states of Georgia, Mississippi, South Carolina & Texas all clearly state that slavery is the main reason they are seceeding. those are their words, not mine.
If you want to read these documents, here is the link
http://americanhistory.about.com/gi/dynamic/offsite.htm?site=http%3A%2F%2Fsunsite.utk.edu%2Fcivil-war%2Freasons.html