Uh, if you believe and are so convinced there is a heaven, then atheists friends of yours are eligible for it, even though they don't believe in it. In short, the afterlife would be "proof" that atheists were wrong (exactly that proof we can't/don't have while here on earth).

Now, Jesus is clear that not everyone gets into the "cool club", but the disagreements (as Life of Brian so clearly and almost effortlessly shows, "follow the gourd!") are what he means by "follow me" or "through me".