>>1
I agree with you that positively stating one way or the other on the subject is a gross misjudgement. That becomes a case of pot-kettle-black. But I think you're missing some key information.
Compare for an instant that God is equivalent to the classical element Aether. At one point it was a widely believed idea that helped make the universe function. Now, it's all well and good to be able to label something that you don't know how it works. But it falls flat when scrutinized. God was given credit for a lot of things in history. But as we chip away we see less and less necessity for a blanket term "God" to help define a why. Especially when the god is not well defined. Aether also was well lauded as a means that things worked in the universe until the time came to put it aside. While it did fill in some gaps, the nature of the structure itself is not well defined.
This is what you may see as "false until proven true". As science has progressed, it has learned to assume the role that if there is no evidence, then you cannot support your claim. It is fine to use your experiences as conjecture. But most people confuse conjecture for theory and theory for fact skipping hypothesis in the middle. So, in a science-y mindset (rational if you will) you must present some evidence that something exists before you can claim it does. Contrast with gravity. We do not fully understand all the mechanics of gravity within the universe but we have evidence of it.
As far as positive atheism (those that claim aloud that there is no god), there are multiple perspectives.
The first group is the usual 16 year old kids who are trying to be anti-conformist. You may find these in high schools or /b/. They brag loudly and proudly that there is no God(s).
Another group says "There is no god" because it is faster and more socially understood amongst rational atheists as "I do not believe there is sufficient evidence to support the existence of any god(s)."
I can understand your frustration with those two groups. It would be confusing to the layman who does believe in a deity where the phrasing doesn't need to be explained -though the question "which one?" should always be at the forefront of your mind-.
I am in the latter group. I do not believe there is sufficient evidence that there is a god. My default position is that I have found all promises of gods lacking in one moral/ethical way or another. I've found all opposition to my way of thinking to lack basic evidence for their cause.
I do not completely throw out the idea of there being a god. I can entertain the idea and would have no major life problems if there were one. I still wouldn't care about them.
If it is a vengeful god, then I want nothing to do with them and will tell them so at the first opportunity. I find this type morally reprehensible.
If it is a loving god, then I have nothing to be concerned about. I merely am using the rational tools a creator gave me to think for myself.
If it is an "deist" style god, then it is indifferent to my existence as much as I am to its. The sun doesn't care about me, makes it so my food grows, gives me warmth, and I see it every day. I'm not going to start worshiping it.
I would be interested if there was ever evidence of a god to exist. I'd certainly have a lot of questions I'd like answered. On the whole though, I've found that everything in my life has not be influenced by greater than chance.
There are other forms of atheists that do exist (Raleans, Buddhists, Negative Atheism, Humanists, etc.) But I can't speak for them. I am not even entirely speaking of the two man groups that bother you. But hopefully, this will give you some perspective.