Strong patriotism does not inherently need to nationalism, but executing people without a real trial inherently leads to the murder of innocent people.
Can we really make any definite statements about nature versus nurture within a culture that has been under a totalitarian regime for centuries? If Germany was a little more successful in World War II would we all think Aryans were just that awesome? How would North Koreans respond if you asked them about democracy?
Maybe the Cardassians are inherently more submissive to authority, more arrogant and conspiratorial. Maybe they're that way because they were raised under a dictatorship, who really knows? But even in the show the average Cardassian civiliian exhibits more fear of their government than respect for it.