You're forgetting that DNA is far from the only input. There's also environment. And you're underestimating the chaotic, nonlinear system that is the material world. We can't accurately predict the weather a month in advance, what makes you think you can accurately predict the life of a human being?
I don't think it's worth the time to argue with these people who conceive of the human body as a "turing machine" and that genes are as simple as "config file".
This is also the guy who says that "Activism does not work. Grand social movements do not work." But I guess the Civil Rights Movement, women's liberation, and the LGBTQ movement don't count?
This is a serious problem I see with many tech / CS inclined people: in which useful abstractions become the map in which they see the territory.
