I think you'll find that 421 carries on working on all contact areas, weeks after treating. So the environment that has it - will benefit, in cutting down on spreading the virus.
Ok, for sure you cannot stop cross contamination between person to person via airborne particles, but this method of treatment is better that having no treatment. So as far as Im concerned, there is no question about ethics, as a job is being done.
If it is sold incorrectly then thats down to the individual.
I suppose the same argument could be said about protection i.e. being realistic in what it can do, and if it is sold correctly. Bet that doesnt stop you selling it though :
Mark