Houston refers to the Panic of 1857 which some blamed on low tariff rates enacted that year. David, opposition to this tariff (North and South) could be predicted. Houston's biographer notes, "He has taken a great interest in the tariff and other practical issues, and has steadfastly opposed extravagant expenditures." Present-day Alabama Congressmen opposed the Health Care Reform Act (AKA Obama-Care). I've yet to learn that any of them believe secession to be a proper countermeasure.
Do you have evidence of the Morrill Tariff being a subject of debate by either of these gentlemen the Alabama Secession Convention? Both were delegates, as noted above.