Well, yes, of course "Could the CSA have won" is a what if. That is kind of obvious.
And when someone says There no way the south COULD have won (emphasis added), I'm sorry, but I disagree, I do think he is falling into the fallacy of thinking they know more than they actually do.
Its not hard to come up with alternative scenarios where the CSA wins. What if Lincoln's ham handed handling of Maryland drives Maryland and Kentucky to secede? What if Lincoln bungles the beginning of the war and instead of uniting the country after Sumter, the north is further split by Lincoln being perceived as the aggressor? What if the Supreme Court rules that secession is legal and the US and Lincoln have no authority to force the states back into the Union, thus destroying northern support for the war? What if Lee cripples a large part of the AOP during the Seven Days and puts it under siege at Harrison's Landing, forcing it to surrender en masse? What if the Monitor sank on the way to Hampton Roads and the Virginia was able to devastate the AOP's troops ships? What if the Lost Order is never lost and Lee ends up crushing McClellan in Pennsylvania? What if the CSA followed up the victory at First Bull Run by following up the retreating US army and capturing DC and most of the US government, including Lincoln? What if the CSA's capture of DC and Lincoln prompts Great Britain and France to recognize the CSA? What if the Trent affair is handled differently and Great Britain invades the north from Canada? What if the CSA defends New Orleans better and does not lose its largest city and a big stretch of Mississippi early in the war? What if Sherman dies at First Bull Run and Grant gets shot and killed at Belmont?
People will say none of that happened. True, but that is the fallacy of it didn't happened, so it couldn't have happened. It would not have taken much for any of the above to happen. I little bad luck here, a little more planning here, and momentous differences occur. That is the nature of war.