There’s that bit in Julia Sweeney’s Letting Go of God in which she tells her mother that she’s an atheist, and her mother replies, “not believing in God is one thing, but an ATHEIST?” — it just tells you how poisoned the word “atheist” had become. It’s gotten better; we’ve been coming out, showing the world we’re just like everyone else, making arguments for a rational, secular morality, and generally working to overcome the prejudice against the label. Imagine an alternative world in which many atheists had followed a different tactic: when ever someone said something disrespectful of atheism, there’d be a mad rush to get their home address and phone number. We’d flood them with threats: if you don’t shut up, we’ll rape your mother and set fire to your house. You’re a whore. I’m going to kill you.
The stigma of atheism would worsen. Now in addition to having a reputation for godlessness (true!), we’d acquire a reputation for truly villainous behavior. People would be even more reluctant to call themselves “atheist”, and only the most vile people would embrace it, worsening the reputation.