"There is also extensive scientific literature on this chemical and no connection to any sort of birth defect has ever been noted."

Weasel words, unfortunately, unbecoming of a scientist.

"Pyriproxifen has been widely used in tick and flea collars for pets for years without any problem. Finally, this particular larvicide's mode of action is interference with the functioning of a hormone that is found only in insects and there is no plausible mechanism by which it can interfere with mammalian physiology in a way that would cause microcephaly."

The world of pharmaceutical research is replete with examples of drugs causing unexpected effects, sometimes even after years of ostensibly trouble-free use. Process dictates that you find problems usually when you are looking for problems. Saying you haven't found a plausible mechanism when you haven't needed to look for a plausible mechanism isn't really good enough. Don't get me wrong - I'm confident that yer man is right. His pronouncements, though, are tendentious-sounding and don't inspire confidence.