So, let's assume that you claim that Bob cheats on his wife while you don't even know if Bob is married. You better prove it while Bob can only roll his eyes at the absurdity of your claim in the interim (especially if he's single, faithful, or celibate). Bob certainly has no obligation to prove you wrong. If anything, he can sue you for libel. And if he’s guilty as charged, the burden of proof is still on you.

Atheists don't usually appeal to Darwinism. It's folks like you who desperately twist themselves into pretzels to validate at least some form of intelligent design (and by extension intelligent creator) who attack Darwinism, because modern synthesis (aka Darwin, Mendel et al.) clearly demonstrated that intelligent design is untenable, hence it pulled the rug from under your rationalizations. You must shoot down Darwinism, because otherwise you have almost no rational ground to stand on. Atheists then merely explain why your criticism holds no water. And of course I would say that “creation” of life as explained by Darwin et al. is heck of an intelligent solution.

Also, your understanding of Brahman is completely off. Its very definition is sat-cit-ananda which means existence-consciousness-bliss, or satyam-jnanam-anantam that is reality-knowledge-infinity. I'm sorry but there's no impersonal universal spirit there. Brahman is neither impersonal nor spirit. That's just preconceived wishful thinking.