I believe that they all exist. That doesn't mean that I worship or agree with them all. Like, most American's would agree that Communism, Socialism, etc. exist, but we don't necessarily agree with their values or what they teach. However, just because we disagree with them doesn't mean that we disregard their existence.
But deities aren't normally defined as abstract sets of ideas developed by people, like Communism, Socialism and so on. They're defined at a minimum as supernatural, sentient entities with varying superhuman powers. What do you mean by their "existing"? Related: would you say the
Flying Spaghetti Monster exists?
If you "believe that they all exist" but you just mean "these concepts of deities exist", that's going to muddle up a lot of people; you wouldn't say "I believe that hobgoblins exist" when you actually mean that yes, there are plenty of people who have very clear ideas of what hobgoblins are like and believe they exist... so that CONCEPT definitely exists.
I'm not sure that's what you're saying; do you think all of these gods exist in the sense that they have ever actually influenced physical reality
separate from the secondary influence of believers?
[...] but what does it matter so long as you are content with what you believe? If they want to "save" me I have to stop/leave/change discussion.
I think most atheists would agree that people have the right to believe what they want to, though that right needs to stop when it infringes on *others'* rights. Unfortunately, many major religions don't include caveats that "the other folks are just as likely to be correct as you are, if not more so". As a result, religious beliefs very quickly start to influence laws, political choices, education, etc. etc., all of which are things you can't just walk away from.
There's more on this earlier in the thread, I think.
Every religion is a door to the same end, and we each have a key. My key fits the door with no scripture, no face, an absence of something to touch and realize. Others have keys to doors with the Torah, or the Bible, or the Koran, or Buddah, or anything else. That doesn't make their key any less real.
We're all born into this world knowing nothing; then we are bombarded with varying (and sometimes conflicting) explanations and models for the functioning of the world from all sides. They aren't all equally valid or even useful based on what we can actually know about the world -- you have to discard many, many bits along the way as you decide what works and what doesn't.
I don't like the metaphor of a door & key, because religion is far more complex than that -- and you can, in fact, pick and choose the useful bits from the non-useful bits in any religion's enormous and multilayered array of beliefs. AND each bit will modify the way you think and interact with the world -- it's not true that any set of beliefs will lead you to the same result. The important thing is to actively evaluate as much as possible.