Atheists may be wrong about the existence of God (at least in my view they are wrong), but that doesn’t mean they are wrong about everything.
No, but her atheism pretty much means that a Republican nominee for national office can't hold her up as a guiding star for his own philosophy. It's a deal-breaker.
I would venture a guess that most atheists believe 2+2=4, and in doing so I agree with them wholeheartedly. Yet, while they may hit upon certain aspects of truth, their very belief system is self limiting.
I don't recall in which which book CS Lewis discussed the matter, but he confronted somebody who asked him about the "truths" that may be found in belief systems other than Christianity.
Lewis likened it to an archaelogical dig. If one starts to unearth a site, and finds a a grainery, a mill and a bakery and properly identifies them as such, they have uncovered a truth and reality: this was a grainery, a mill and a bakery. All evidence is that they were a grainery, a mill and a bakery and any theory or notion otherwise can be easily refuted. One can boldy assert these are what they are with absolute confidence. However, any assumptions or extraplations above and beyond the limited "truth" will almost certainly be flawed. For example, to conclude these were the work of a peaceful, agrarian people based on the identification of a grainery, a mill and a bakery would lead one to a very flawed understanding when further excavation reveals that these were merely the logistic support for an extensive, heavily fortified and armed military training camp.
Lewis contends that Christianity offers the holistic, comprehensive "truth", and that while other belief systems may uncover elements of it here and there, Christianity alone reveals it in its entirety.
I think it's a good analogy for Rand, who hit a few key things dead on, but made a few flawed leaps in stringing them together.