What exactly is heresy?

In the last few weeks, the Bishop of Portland campaigned heavily, and even funded (probably at risk of the Church's non-profit status) the campaign to overturn the gay marriage law. This invited organized opposition from a group of organized Catholics, who campaigned against the referendum.

In prior years, this would have been considered unthinkable. Most believers were not well educated and took the bishop's word to be law. Nowadays, many Catholics have college educations and even training in the same philosophy programs most seminarians take. Quite a few others also have taken public policy courses at the undergraduate and graduate levels and find it laughable that theology majors are telling us how to vote.

We are required to act from well formed consciouses. However, in some areas, such as public policy, it could be argued that our conciouses have undergone better formation, especially in democratic societies. Some of us also know a bit more about human sexuality, (both the psychological aspects and the biological processes) through training and experience. Again, such knowledge is as much part of the formation of the conscious as the teachings of the Church, especially when in matters sexual teaching is developed by a celibate clergy whose celibacy evolved from the rather obnoxious belief that one could not engage in sexual intercourse and then celibrate the Eucharist too soon (a belief that the Eastern Church finds anethema).
The question arises, is disagreement with the Church in these areas really considered heresy when our information was better? Galileo was better informed. Did he have a right to be defiant when it was obvious that the Church was wrong?

Is it servant leadership to insist that you are always right? Jesus washed the feet of his disciples and commented how worldly leaders lord their position over their subjects, which echoes what he told James and John when Salome (Jesus big sister from Joseph's first marriage) goaded them into asking for seats on his right and left. Are the bishops acting in this spirit when or as secular rulers when they insist they must always be right - even when those that disagree with them have better information?

Perhaps we need to define heresy only in terms of theological belief - and even then we need to be careful that the belief in question is really essential. Esoteric beliefs about the Trinity (such as the Filioque, or even the difference between consubstantiation and transubstantiation) should probably be open for debate. Certain beliefs, such as the divinity of Jesus and the fact of the resurrection, are essential since without them there is no reason for faith. Let's keep charges of heresy to what is essential and keep an open mind about the rest.

I am not arguing here for relativism. Relativism says that you can make up your own mind about everything. Instead, I am arguing that there is such a thing as truth, but on occassion it must be sought outside the hallowed halls of the Vatican. As time goes on, I believe such perspective will be more widely expected. Indeed, the survival of the Church depends on it. Since the Church is promised to survive (although not necessarily the way it is governed from Rome), I think it eventually will come out alright, even if it is hard for some.