I find it hard to call Protestants real Christians. Most denominations tend to really dumb down everything about the Faith. The way I see it, the real Christians are the Catholics and Orthodoxy. Of course, I'm biased.
All denominations are Christians by definition.
By an inadequate secular definition, sure. Look, if I call myself a Christian but then refuse to acknowledge parts of the Bible, can I still call myself a Christian? What if I refuse to acknowledge the Bible altogether? At some point, you can't truthfully call yourself a Christian. I know where I and the Catholic Church draw the line. Where do you?