Poppycock. The Wikipedia page lists a small handful of promising technologies[0], and there are others not listed there: improvements in organ transplantation and/or cloning would do wonders. I'm particularly fond of the idea of synthetic chloride channels that do the work of the CFTR protein.

But the reason that cystic fibrosis is lethal is because of the mucous. The lethality of the mucous is unrelated to your lifestyle choices, since the lungs of a CF patient are colonized by bacteria that prefer the different type of mucous. This sort of thing is exacerbated by fraternizing with other people who have CF, since they're likely to infect one another.

Over time, the bacteria become resistant to the antibiotics used to treat the disease. So more antibiotics are definitely in order, although that's not the be-all end-all. Again, I'm just saying that lifestyle interventions are almost certainly not effective (I can't even see how).

But there's a critical point in here: sure, Ignaz Semmelweis was laughed at for positing an unusual theory. But so were tens of thousands of others who came up with actually crazy ideas, too many to list. All I'm saying is, just because people disagree with you doesn't mean they're wrong.

[0]https://en.wikipedia.org/wiki/Cystic_fibrosis#Research