I get what he's saying, and in many ways I agree, but the choice of words is too strong for the hypotheses he's presenting. For example, he uses the following to bolster his claim

Abundant evidence indicates that people who grew up in homes marked by chaos and deprivation will perceive the world differently and make different choices than people raised in safe, stable, resource-rich environments.

Yet he mentions himself that we are subject to our external environment. Some of these individuals do not make markedly different choices based on these external differences, not to mention their own internal ones (genetics, etc.).

To make the claim that we have no free will because we are the sum of our environment + upbringing ignores that we have a modicum of control over our environment, and it also ignores how our interactions provide that external environment. We pass laws to further human rights and create a better environment so that people in the future would hold them in higher esteem and be influenced by these choices we make. In short, there is a field of possibility that lies within the maybes - our genetics and upbringing set us up for how malleable we are on any decision. Some decisions simply won't happen and some outcomes are likely inevitable, but most fall in the space where there is a likely but not predetermined outcome which is influenced by the environment. This is why perfect predetermination is impossible.

In fact, this very viewpoint is even reinforced in the most physical of sciences - physics. In quantum physics we can at best determine probable outcomes. While there are theorists who believe in superdeterminism, or the idea that we simply don't have all the variables to determine everything perfectly yet, superdeterminism has gotten no closer to explaining bell tests, the slit experiment, or other quantum phenomenon in well over 50 years. Increasingly complicated mathematics repeatedly show that there is a fundamental randomness to the universe that we seem unable to capture.

And I think it makes sense, in the context of what we know of biology and evolution. Brains are constructed in a way where signals are created almost randomly, and then organized to make sense of the world. Evolution has played a part to refine this processing so that it ignores what's not important to survival and proliferation. If this process weren't generative and random in some sense, we would not evolve and there would be little to no purpose for diversity. The world is constantly changing and thus our biology must account for this, meaning that it must be malleable and open to changes by the environment. If it is open to changes by the environment, then we must be able to influence each other and thus a concept of free will must exist that at the very least is a representation of the sum of all that activity.