I think a good number of atheists don’t argue to try to convert people away from religion, but to make themselves feel good about their non-belief, which is much more rational, from their perspective.
Let’s face it, if you’re a believer in religion, you’ve probably heard all the logical arguments against it, and still choose to believe. So nothing an atheist is going to say to you is going to change your mind anyway.
It’s not a list of reasons why you should convert away from religion, it’s a set of obstacles which prevent me from converting to your religion.
If you, for example, do not have a problem with the entire tale of Noah’s Ark, from spectacularly silly start to spectacularly silly finish, then there is absolutely nothing that can be said to persuade you to stop believing in it.
Me, I have a problem with it, and the whole rest of the tale, and the church, and the doctrine, and the cherry-picked moral message of the modern age which is mostly don’t have sex until marriage, don’t get divorced, and gay is teh evilz.
So I can sit here all day and list all the reasons why I think you’re silly for believing, but really, honestly? It will always be more a list of reasons why I would feel completely silly if I believed in that stuff, and it’s preventing me from ever thinking that it is anything but a waste of one’s time.
I don’t think I’ve ever come across someone who believed they could be debated or argued out of religion, and I’ve never really believed I could convince someone. If someone believes in the world’s oldest placebo, there’s no amount of medical studies which will sway them otherwise.