At the end, he says he covers the scriptural basis of his conclusions in a 6-part series on YouTube. I wasn't really impressed with that either. Beside no real good scriptural basis for rejecting Calvinism, Dr Walls presentation is flawed because the philosophy underlying it is flawed. For example, he spends quite a bit of time on talking about Calvinists must accept the compatibilistic interpretation and definition of free will in order for Calvinism to be consistent. I disagree. If without salvation, you are enslaved to sin and can't choose not to sin that would mean you have not the ability to do otherwise and Libertarian Free Will falls with a thud. This does not mean that people don't have wills of their own. We do. They are just bent and broken. Jesus is the only way to be free. I agree with James White, there is free will - only it's God that has it.
Thoughts from the Boonies: Jerry Walls: What's Wrong With Calvinism