"Baptism, "the way to enter the club"? I guess it was J. "I am the way" Christ."
Well, you are wrong, then.
"Baptism is more like the club's bumper sticker."
No, it isn't.
In the Catholic dogma, sacraments are so called "effective": they do exactly what they say -they are not just a sign of what happens but the way to make the thing to happen or the thing happening itself.
And then, baptism is considered one of the three sacraments with "character", which means they imprint on the soul an indelible sign: you forcibly need to be baptised to become Christian, being no other way to become Christian, and once that you get baptised you can't be "debaptised": you'll be forever a Christian even in case of apostasy -you rebel of what you are but you can't stop being what you are.