I tried going to the Christian Fellowship thing at my school a few times... One time, a friend of mine who's into the punk sort of scene walked by and flashed them a hand sign that she told me later was a 'devil sign' to rattle them - the joke is that they didn't see it because they were too busy loudly agreeing with each other that all [insert reviled denomination here]s are misguided and are going to Hell.
And then, one other time, I went, and there was a talk about 'witnessing' and 'testimonies' and there was all this Christian terminology... I tried to pay attention, and at one point I was thinking "You're technically speaking English, but I am not understanding." I came up to the main person later and told them in a fairly even, non-threatening tone that I didn't understand, and could they please explain these terms, and they went off at me, and strongly implied that it was my fault that I didn't understand. No explanation, just blame-laying.