How can a person be a heretic in one culture, but not in another?

The simple answer is usually religion based or a cultural difference in belief.

Explanation:

For example while one religion may allow priest to get married another may not rendering the person a heretic in one and not the other due to religious difference. Culturally speaking usually a person is not a heretic however, one could say that for instance in Japan it's rude to talk or make noise on the subway system while in New York that is not the case. This cultural difference if played into may make you seem like a heretic to the Japanese and not to the Americans.