Strawman arguments, you have setup multiple claims about what atheists believe and NONE are correct. Atheists reject the claim that a god exists. A person that is skeptical about life on other planets, abiogenesis, the multiverse, etc. ARE STILL ATHEISTS!
But since you asked, I dismiss the claim that god exists because of the lack of evidence. I also withhold my belief about life on other worlds for the same reason. I think it is possible but until they find it, like every atheist I know, I withhold belief. We may accept the unlikeliness of life not being somewhere else in the Universe, but that is not the same a belief.
The concept of multiverse is not generally accepted, it has been shown to be mathematically consistent but I await further proof, which might not even be possible to obtain. That is also the opinion of most scientists, even ones working on trying to prove the hypothesis.
We know that abiogenesis happened, somewhere, but we haven't worked out the mechanics yet. But we have proven that organic molecules including amino acids can arise from non organic means. It has been done in laboratory conditions.
There is NO logical argument for god that is both sound and valid, none. Every attempt, from the Kalām cosmological argument to Pascal's Wager, they all fail. So your assertion that atheists refuse to accept these "validated arguments," is another strawman. No valid arguments exist.