The Gods of the FR are far more like the Norse or Greek Pantheon. Fallible, emotional and all too human. I’m sure they consider a mere human claiming to deny their very existence something deserving of punishment.
The Wall of the Faithless is a punishment for those who deny the gods or are false in the name. Why, in a world with real gods would you think their
wouldn’t be a punishment for this? It’s not about fairness or justice, it’s about those in power protecting their hegemony. Not to mention the fact as Ed G says, not believing in the gods in the FR is clearly idiocy.
In short, to answer the OP, yes there are lots of people who have no problem defending the Wall of the Faithless!
As to the Cataclysm... never heard of it... what’s a Dragonlance?