Never said it was a good suggestion, just that it was a solution to the parasite insect issue. It does not address other disease issues brought forth by wild birds (newcastles, anyone?)
As a side-note, this is not a slippery slope type issue (At least, not as I have heard the term defined as)...
Dusting one nest is not going to alter the local insect population significantly, period. Now if they were dusting the whole run, that would be a different story.