b: "I'm a free thinker"
b: "I'm not really sure whether god exists"
a: "So you're agnostic?"
b: "No, I'm a free thinker"
a: "That's a little vague; you could be a free thinking atheist or free thinking agnostic but saying free thinker doesn't tell anyone what you believe in"
b: "But I'm a free thinker"
a: "Do you even know what that means?"
b: "My friends are free thinkers"
Despite what the term actually means, it is used by condescending people to describe themselves.
The irony of people who refer to themselves as freethinkers is that even though they believe they formed their opinions solely on reason and science, modern psychology disproves that people are capable of that.