I have been coming to the conclusion that the Latin Church views heresy somewhat differently than Orthodoxy does. By your definition, Arianism, Nestorianism, Sabellianism, Montanism, Donatism, etc. etc. would not have qualified as heresies yet the Fathers and the councils condemned and anathemized them as heretics. When you look at their theology (except maybe the Arians and the Montanists in my list)and even more so their praxis (except perhaps the Montanists)what you see is in most senses the orthopraxis of The Church.
When we in Orthodoxy look at "Protestantism" we see, even in its wide diversity, very little which looks like the Faith of The Church except in some basic Trinitarian and Christologic theology. We see virtually nothing of the Mysteria or liturgical praxis; we see virtually nothing of Holy Tradition. Its sotierology is almost completely different from ours. To us that spells heresy and heretics.
On the other hand, it is interesting and I think informative to remember that Arians, for example, were received into The Church by a simple profession of Faith, sometimes with and sometimes without chrismation which speaks volumes about what The Church thought of Arian baptism, for example.
Sitting in the East and observing the confusion of Western Christianity, we have to conclude that when the Protestants did leave the Latin Church, they did indeed take a great deal with them including a sort of proto resistence to the pyramidal ecclesiology and the marginalization of the laity and lower clergy from the workings of The Church in the West. To tell you the truth, I think that in many senses the Protestants have a better intuitive understanding of the fullness of The Church, or better put, where that fullness is found, than the Latin Church does, even if what they have created don't actually qualify as churches because of the truly astonishing amount of the Truth of The Church they rejected and left behind.
These were all genuine heresies because they did not focus on a truth, somewhat out of proportion, but invented or denied fundamental doctrines and then asserted their inventions to be the true doctrine of the Church. They did not plan on going off on their own; they wanted to impose their doctrine throughout the Church, and in a couple of cases, they very nearly did so.
Classical Protestants, on the other hand, are a little more pragmatic, if one may say that, often rejecting something that was perhaps an overemphasis in the first place and rejecting practices or structural things. And, of course, they separate themselves and set off on their own, which, paradoxically, is why it is easier to reconcile them with the fullness of the Faith when they decide to come back.
The danger, of course, is that once Protestants are "launched" on their own little splinters, even the splinters splinter, and in some cases, they are left with a fragment that is no longer even recognizable as the truth. Non-Trinitarian Protestants and those groups that that have devolved into vague deist sects would be an example of this. And then there is also the risk of the development of personal "revelations" based on their fragment of the truth, such as Joseph Smith's "revelations" that led to the founding of the Mormons, a group that I think is trying to work its way back to orthodox Christianity but certainly was initially very far from it.
I don't see how the "every man his own church" system has anything in common with the Orthodox understanding of the Church, btw!
As it well should...There are folks on both sides who look at it as one big disgruntled family...And in the case of many Protestant groups, that may be correct...
But as in the case of Southern Baptists for example, the gulf is too wide...Your side and their side teach and believe in different roads to salvation...And they are NOT both correct or acceptable...One side is going to be sorely disappointed at the Judgement...
I've been called a heretic by Catholics...And after researching both sides, I'll wear that 'heretic' moniker proudly...
I agree from the other side of the fence. And we don't have too many nice words talking about your side either: ;-) From our side, those of the more more-spoken people classify you as "Aberrational, Heretical, Heterodox, Suborthodox or Unorthodox" which is the same classifications the Roman Catholics get.
http://www.apologeticsindex.org/o06.html
http://www.namb.net/evangelism/iev/PDF/BB_E_Orthodox_Manual.pdf
Some of the more extreme words from our camp would be along these lines:
http://www.wayoflife.org/fbns/eastern.htm
"...From these quotes it is obvious that the Orthodox Church is entirely apostate. It holds the same basic set of false beliefs as the Roman Catholic Church from which it broke away in the ninth century."
Just a different perspective from "our side". ;-)