Atheism is a belief system, however someone defines it for themselves.
So if someone asked you if Santa Claus was real you would say it is your BELIEF that he is not? Easter Bunny same? Tooth Fairy?
Atheism requires a belief there is no god
So in your world people commonly have to prove negatives?
You only have a BELIEF that an invisible sasquatch doesn't live in your back yard. Right?
What I don't get is why Atheists are so upset when someone points out that their beliefs amount to a religious system.
Probably because in our world words have meaning. It is clear that in your world words mean whatever you want them to mean. So in your world hobbies include NOT golfing. NOT playing football. NOT collecting stamps.
Atheists don't actually know that a god doesn't exis
Correct. But it is incumbent upon the believer to provide evidence that he does. That's how it works.
You don't KNOW that the toothfairy doesn't exist, do you?
Now, if you don't give a shit about whether there is a god or not, then just call yourself a "secularist" because that is accurate.
Your lack of knowledge of atheism at a technical level does not put you in a position to define what is accurate or not about the topic.
Religion is irrelevant to you and the debate is over. The worst is an Atheist, that pisses and moans about their belief there is no god being called a religion. They are lying to themselves for some idiot reason.
"Some idiot reason" is the very same reason that you don't believe in Santa Claus. It isn't a "belief" for you that the tooth fairy doesn't exist.
So that "idiot reason" is the exact same one YOU use in your daily life.