If I were All-Holy like the Lord, or even mundanely holy like a saint, I guess calling people "vipers" would be OK. Since I'm obviously not, I'm more comfortable using the "fellow sinner" approach.
That's what you say when they're getting a Dell. "Fellow sinners" is terminology you use for people who recognize they are in sin, or at least subject to sin. When someone is trying to indoctrinate your children, you bring out the millstone rhetoric.