Why, you ask? Well, as Tim Perry might say, we, as Protestants, are all schismatics. But that’ s not really what I’m getting at.
What I am getting at is this: heresy, it seems to me (correct me if I’m wrong), has to do with departing from the church’s official teaching . Prior to the Reformation it was quite easy to say, “This is heretical belief” because there was one church (I’m speaking purely of the West). Now that X number of denominations have been established and we’ve got splits of splits of splits, it’s not clear to me how we can speak of “official church teaching” in any way apart from the ecumenical creeds.
As a result, for a Reformed type to call an Arminian, for instance, a “heretic”; or a Baptist to call a Pentecostal a “heretic”, apart from Creedal doctrines, is really quite moot. Apart from the Creeds, the denominations are nuanced in a way that puts them in different theological camps. Prior to the Reformation, and post-Great Schism, the same might be said of Roman Catholics and Eastern Orthodox.
Don’t get me wrong–I believe in “the one, holy, catholic church”–but we are no longer in a position where one particular theological position can claim to be the voice of the Church Universal. There is no one theological scheme that can be turned to as the litmus test for orthodoxy.
The term “heresy”, therefore, really only applies to those who claim to be among your particular Christian sect.
Which is why, in my opinion, the notion of Rob Bell’s reformed detractors dropping the word “heresy” in terms of what he (allegedly) believes is really quite silly, because from what I know, Bell isn’t claiming to be one of them.