What are people who were avoid and called heretics?

To answer this question, we must first understand the implications of their definitions.

A heretic is a person who practices heresy; heresy is belief or opinion that is contrary and deviates from mainstream, or orthodox doctrine. It usually applies to Christianity.

This happened mostly in the middle-ages and renaissance era, but most prominently during the Protestant Reform from the Catholic Church.

At the time, the Catholic Church was the main religious institution in the Western world, and held tremendous influence. Some people began to believe that the Catholic Church had become hypocritical, fraudulent and corrupt, (for good reason), and decided to reform.

Such leaders as Martin Luther and others started this "heretical" revolution, and churches that spring from this are Lutheran, Methodist, Baptist, Adventist, Anglican, Pentecostal etc.

In effect, people who were "avoided" and "called heretics" were those who, historically, disagreed with the Catholic Church in any way.