Why do people pity smokers?

Ive awalys wondered why people would seriously waste their time talking about friends or people they see who were smoking. These anti-smokers/Health nazis seem to pity and consider themselfs better than smokers. Why can't people just let others do what they want with their lifes and let them do what they wish, drugs, cigarettes.. whatever. If they pity them so much why do they awalys talk behind their back in disgust. Just let it be..?