Even though all of the Protestants (with a few exceptions) have dumped the sacraments, have accused us of heresy and have been absolute _____ sorts of people;
Even before I became Orthodox, somewhere during my journey I began to think it kind of strange for Protestants (i.e., primarily those of the "Evangelical" or non-denominational variety) to use the words "heretic" and "heresy."
I mean, what can they use for a standard?
They can't use the Creeds, because those were written by Bishops who believed in the bread and wine becoming the body and blood of Jesus and in the salvific effect of baptism.
They can't unhesitatingly use the Bible (though they do all the time), because the books that were chosen to be included therein or excluded therefrom were not simply self-testifying, but were to some extent (the "disputed" ones at least) ratified and agreed on by those same non-Protestant/anti-Protestant bishops and sacramental Christians. Or at the very least, they can't tell other Christians what books to include or not include in the Canon. I mean, if someone wanted to exclude James or Revelation, on what basis would they say "You can't do that!"? Plus, there is Martin Luther's precedent for nearly doing just that.
They can't say that Arians and Nestorians, etc., or their modern-day counterparts are heretics, because they don't believe in Church Councils having authority to tell individuals what the Bible and the Faith teach about Christology and the Trinity.
Sure, they use the terms the way we do - i.e., to apply to persons who hold themselves out to be Christian but who in some form or fashion teach contrary to the defined teaching of the church. But then get them to define what they mean by "the Church" and what puts someone in the Church and what puts someone out of the Church.
That might make for an interesting discussion. Ask them. Ask them for the basis for their answers. They'll probably quote you book, chapter and verse. Then ask them why they use the Bible - and specifically the 27-book-New-Testament Protestant Bible - to make their argument.