That's a great example that explains the effects of both genetics and environment and has given me a better mental model for these things. Thanks!
I think part of the issue is one side or the other is arguing for an ultimate cause. Taking your example, if no interventions are used, a person with a certain genetic disposition will develop hemochromatosis.
The person arguing for the environmental factors would say something like "Yes, but for any disease chalked up to genetics there is a theoretical intervention* that does not manipulate genes and still cures the disease. And it all comes down to environment anyway because look at what happens to people who are exposed to high levels of iron without the genetic predisposition."
To which the person in favour of the gene's eye view can say "Yes, but for any disease chalked up to the environment there is a theoretical intervention* that only manipulates genes and still cures the disease."
I agree distinctions are starting to sound pretty meaningless at this point. Though I hope that should clarify my position.
*At least in all but the most extreme cases
I think this is a very good illustrations with the following disclaimer. Unlike the genetic argument, which so far has relied on pretty much entirely theoretical arguments for interventions yet to come, the environmental argument has produced some results and drugs that do not manipulate genes but still work. Dietary interventions are also beginning to show results. Again, it comes down to results and complexity. The genetic explanation was at the forefront of medicine for more than 60 years and produced absolutely nothing in terms of therapy. The metabolic/environmental explanation is just starting to take hold and it already has results. So, thus far, the environmental argument has more weight on its side. Why add the extra theoretical framework that genes are involved in disease when it adds nothing of value for two reasons: 1) apparently environment controls expression to the point of negating heavily genetic features like height advantage in a single generation simply based on diet; 2) no genetic therapeutic results so far and no specific genes discovered to point fingers at for the most common chronic conditions despite decades of effort.
Again, I am not against genes, I am simply saying that so far the evidence for the role of genes in most diseases is sorely lacking despite 60+ years of serious efforts and good funding in that direction. I am excluding conditions like phenylketonuria, Down syndrome, hemophilia, etc for which the genetic role is very hard to dispute.