Smoking causes many adverse health effects, including heart disease. Cardiovascular exercise and smoking are two activities which fall at opposite ends of the health spectrum. Cardiovascular fitness, or cardio, helps to improve heart and lung function, builds athletic endurance, and promotes overall health.
When you understand that the person you are talking with is unable to shift his/her opinion, and starts getting mad. That's the best time to compromise, since not doing so might bring stress and conflict as you mentioned.
