Actually this is an excellent question and I for one would like to know the answer. The one thing I know is that BHT has been taken by many people including myself for a good number of years to fight off viruses without any ill effects. I do believe that more thorough studies on this subject should be made especially in reference to the point you just brought up.
Well, my guess would be it is damaging your own cells too, but your cells have the capacity to regenerate or replicate themselves, while viruses do not. So it’s like a war of attrition.
bht is an antioxidant
its a regularly used ingredient in the food processing industry
its kind of like asking why coq10 wont kill you, or any other antioxidant you take or eat in food won’t
it goes after the oxidative damage in your body, it helps keep inflammation down, it basically stops you “rusting”/breaking down on the inside