I didn't drag it in. You did. I responded to what you said about "undecided". Here are your words,
"What if one person says "I don't believe they exist and I don't believe they don't exist either I'm undecided..." and another person says "I believe they don't exist" do you really think they say the same thing?"
In your example the first person is not an atheist. They are agnostic. The second person is an atheist. So do you agree with this, since you just acknowledged that undecided means agnostic?