Maize said:
"If you don't serve my God, you serve Satan"
I've heard this line more than once from certain groups. Do you agree with this statement, or is it hurtful and detrimental to the user's overall message and to whom it is said?
Short answer: No. It hurts the person/group.
Long answer, I i believe things like one God, one Church, one Christ, etc. It is true, that when someone isn't serving the Christ in His Church, the two interests cannot be the same simply by definition. Christ did say, "whoever does not sow scatters, etc."
That doesn't mean that the person is actively deciding to "serve Satan." It is human nature to want to do good, and not evil. None of us want to be on the "evil" side of the fence. Telling someone that they're serving Satan, then, is a judgement on their motives, and most people do honestly believe what they say.
So, doing that gets in the way of any fruitful dialogue between two groups IMO and should generally be discouraged. After all, who am I more likely to have a meaninful discussion with: the guy that I treat nice, eat pizza with, and shoot the bull with, or the one that I approach as a servant of Satan?