Everything about their argument is stupid and regressive and part of a shoddly orchestrated attempt to restore slavery to America and to take away the rights of anybody other than wealthy white men to vote or own property.
But if it were argued in good faith, this one point is a point that makes sense to me, that likely not every person who fought for the Confederacy was a racist, there were likely a few of them who fought to "protect their way of life" not knowing that they were fighting to keep slaves enslaved.
Even with saying that, the grand majority of them, I'm willing to wager 97% or more of them, were by all accounts racist and were fighting to maintain their claim to white superiority.