Repressors—people who unconsciously inhibit their display of emotion—exhibit significant increases in heart rate when they encounter emotion-provoking situations.
Conclusion
The act of inhibiting displays of emotion (consciously or unconsciously) causes a sharp rise in heart rate.
Evidence
People who unconsciously inhibit emotion (repressors) have a sharp rise in heart rate when they encounter emotion-provoking situations.
People who consciously inhibit emotion (nonrepressors) also have a sharp rise in heart rate when they encounter emotion-provoking situations.
Evaluate
This argument seems pretty logically sound on first read, so I would shift into Debate mode to figure out where the wiggle room is.
Given that ... both conscious and unconscious inhibitors have a sharp rise in heart rate when they encounter emotion-provoking situations,
How could we argue that ... the act of inhibiting emotion does not cause a sharp rise in heart rate?
I guess we would have to explain the rise in heart rate some other way. Maybe the emotion-provoking situation is something that causes fear or anger, and fear / anger cause your heart rate to rise. Whether or not you show emotion or repress emotion doesn't actually make a difference.
If your boss is chewing you out, your heart rate will spike. The fact that some people are consciously or unconsciously hiding their emotional reaction is just part of how they're reacting to the situation, but the heart rate spike is caused by the situation, not by their conscious/unconscious decision to repress their emotions.