The 1st premise is...everything that begins to exist has a cause....God is timeless, therefore eternal. If something is eternal then it did not begin to exist. If something doesn't begin to exist then it doesnt have a cause.
Common misconception. A mega-god, if it exists, would have created your local version. So He is certainly not eternal. For all anyone knows, it is mega, mega and more mega all the way down.
Try again?
Interesting argument, could you unpack it a little?
Honestly, I don't do debate. Be my guest.
I didn't want to tromp over you by unpacking your argument. Thanks for your permission to do so.
If I understand you correctly, what you are suggesting is that we could posit an "ultimate supreme being" USB that is infinitely powerful, knowledgeable and so on.
That USB could conceivably create a being that was minimally capable of creating the universe (ie not able to do anything else than is necessary to produce us and everything around us).
Similarly, the USB could conceivably create a being that was minimally capable of being able to create the being that was minimally capable of creating the universe.
And so on down an infinite chain of slightly greater beings.
Each of these beings (with the possible exception of the USB), as you point out, would have a beginning. Since this isn't conceptually impossible, then it is not conceptually impossible for the god of LionIRC and Rostos to have had a beginning. It'd be no more than dogma that their god was beginningless (or timeless or eternal).
Similarly, if the USB is so powerful, etc etc, then it would be entirely possible for that USB to snuff out any of these beings at any point. (For example, it could notice the hissy fit leading to Noah's flood and think "I'm going to have to decommission that sub-god, it's playing up again".) Therefore, it's entirely possible that there was a god of LionIRC and Rostos, that even did the whole short-order universe creation thing, had the Eden arrangement, flooded the Earth because people were being naughty and was smited by its superior (a "mega-god" as you put it). Then a more senior, but deistically inclined god came along, fixed the universe to make it more natural - precisely like the universe wasn't created at all, but rather developed over billions of years - and buggered off.
This would even explain the Moses encounter, given the Dunning-Kruger effect (I'm the best god, don't listen to the rest).
But even if we consider a more vanilla version of this scenario, what you have is an effectively infinite divide between the ultimately responsible creator god and the local creator god. This unpacking, or infinite expansion of gods effectively makes the concept incoherent, I agree. But what theist might not be able to argue convincingly is why, once they have posited an infinitely powerful (etc) god, this scenario is impossible - they trigger the scenario, even if it was us (as atheists) who noticed it.
The idea that LionIRC (and possibly Rostos, but I don't know that LionIRC can talk for Rostos) would turn his back on his creator and worship instead some hugely distant being that probably doesn't care is bizarre and, I would have thought, insulting. It'd be like some schmuck on the production line being given a raise by his line manager and then kneeling down and prostrating himself before the altar of Donald Drumpf, because the Old Double D happens to be his boss' boss' boss' boss' boss' boss' boss' boss' boss' boss' boss.