schismatics, heretics, pagans, infidels
Contrary to "DetlefK" ignorant claim, those words aren't used much in Evangelical Christian circles. The words all have meanings much less lurid than the image he's trying to conjure, but they just don't enter into teaching and discussion that much.
"Infidels" seems more associated with Muslims; an equivalent that is used among Christians would be "unbeliever". But "unbeliever" is a descriptive word, not an epithet or mockery. And much as "DetlefK" would reject it - based on the tone of his post - "unbeliever" is usually used to express love, concern, and caring for people Christians see as having a need (a need they themselves once had).
"Schismatic" is used very occasionally, I believe, among Catholics to describe some person or group who has split off from the Catholic Church. It's kind of an ivory-tower level word rather than a pew-level word. I suppose, being a Protestant, that I could be called a "schismatic".
"Heretic" or "Heresy" are used occasionally among Evangelicals, usually in some apologetics context. I think the same is true among Catholics. It's not used as an epithet or insult. It's a word that refers to a teaching or teacher of same that is contrary to Christian teaching and is causing division in a congregation or among Christians more generally.
"Pagan" is also used occasionally among Evangelicals, usually in reference to people who have thus self-identified.
I doubt "DetlefK" is around enough Christians often enough to know how we speak.