The person who challenged “Define win” suggests a good point. Winning implies victory, and defeat on the other side. Don’t think of it as winning. Think of it as success. You can’t win in the sense of convincing a die-hard theist. (I don’t call them believers. We are all believers. Some of us just don’t believe in things that are not so, and especially not in sheer nonsense.) What you can do is plant a seed. Plant it and be content, then close the door.
If the door-knockers really offend you, and they’ve come with children in tow, I have a cure. “Those are lovely children, and I’m sure you love them very much. Why are you telling them things that simply are not true? And why would you frighten them with stories about a supposedly loving god who has a hell waiting for them if they don’t measure up? You see, I believe you are damaging those beautiful children, and because I love them as I love all people, it pains me to see it. You think about that, have a good day, and come back someday if you’re really prepared to discuss these matters with an open mind and a respect for other points of view.”
It won’t convince them in that moment, but I guarantee you they’ll be listening, they’ll be mad as hell, and they’ll be talking to their kids. The kids, in turn, will see what love really looks like if you do it with kindness and a real spirit of Love; they’ll also see the fear and defensiveness in their parents’ response. And I doubt those same people will bother you again unless you’ve managed to open their minds.