Read Diane Duane's "Spock's World". It goes to great lengths to correct the error you're making.

Among other things, it suggests that the word usually translated as "suppression of emotion" actually means something closer to "passion's mastery", and that the Vulcan ethos is to recognize and compensate for emotions instead of, as many seem to believe, denying them.

Also, as awesome as Kai is, Data is clearly a better example of a functioning rational being without emotions. Data isn't lacking in preferences, goals, and motivations. But he does lack specific, complex states that humans possess. He is perfectly capable of being wary around a danger, but he lacks fear. He has ethical principles and will kill to enact them if necessary, but he neither becomes angry nor experiences hatred.