You have a selection bias going on, there. You will tend to notice the “whiny ones” more often, because they are whiny. This is the same reason as to why, to you, it’s not obvious that it’s not a religion.

You’re also going line by line on the comment which I should tell you is omega cringe and completely misses the main thesis of the comment in exchange for being kind of smarmy and quippy, which I would say is very unchristlike. Their point is that self-identifying as christian is a positive group, it’s a group you choose to identify as. Being an atheist is something you are because you don’t identify as belonging to any religion, it’s a negative group. Atheists are the non-black non-ravens, they constitute literally everything that isn’t. Which one do you think would be the more coherent, singular group, there? It’s like if you had a classification of all chairs being, things with four legs that you sit on. Atheists, in this metaphor, would be everything that isn’t a chair. Even with that shitty definition of a chair, that includes horses, chairs will still be a more coherent and singular group, than “everything that isn’t a chair”. That’s their point.