A heresy is a doctrine which contradicts the church teachings. For example believing that the Spirit proceeds from the Father and the Son, refusing the veneration of icons etc. Heresy has nothing to do with being cruel, honest, dishonest, kindhearted and so on. Someone believing in a heresy is a heretic.
According to our Bulwark of Orthodoxy Saint Gregory Palamas, the Holy Spirit proceeds from both the Father and the Son but in different ways. Is he a heretic? I think not! As for the veneration of icons, it is a tradition that was needed in the Greek world but maybe not in the Germanic. (I try to have a Christian understanding towards others).
The belief that an icon is a graven image is a misinterpretation, but I still don't think it can be considered a heresy since the Evangelicals have many good fruits, even though the fruits of the Muslims on the other hand, is not so good. But I don't think that's related to their ban on graven images? As for me personally, I believe a graven image is making an image of the demon we worship, such as money, power, prestige, fame, etc., etc. Pagans always did, and the ancient Greeks went even further and gave them human form. Kind of creative there!
As for a heresy I should think it would be a state of mind leading one away from God and that can only be judged by it's fruits. So what are the fruits, wouldn't they be cruelty, dishonesty, immorality, etc., etc. Of course if someone teaches something that keeps them away from the fruits of the Holy Spirit then it definitely should be condemned. If on the other hand, the fruits are charity, love, kindness, compassion, etc., etc, then how can it be a heresy? Wouldn't that be an oxymoron?