Reading everyones notes on this subject has made me think of a good response for your neighbor.

Whenever he mentiones his chemical use, whether it is spraying or the exterminator, just ask him how much it costs. Then respond by shaking your head like your mistified, and just say "wow", or "that much, huh?". Even if he comes back with "Oh thats nothing for what it does!" just nod. Then he gets to look at your beautiful (free) yard and stew. EVERYONE hates to get it in the pocketbook! So whenever he throws a dig in about chemicals, you toss a dollar sighn back at 'em.
Fun thread!]
Bada

Thanks so much to everyone who replied to my posting! Lots of great suggestions! I think I will end up doing what most of you suggested - ignoring it. I don't want to cause bad blood and if just knowing that I'm organic causes him to be so annoyed that he can't control his comments, I'm afraid that if I acknowledge them (the comments) at all, they would just escalate. I will keep quiet, and remembering some of the suggestions in this thread, I will smile an enigmatic smile and let him wonder what I'm thinking. At least I don't have to worry that I'm poisoning MY kids! Thanks again to everyone. This is such a cool site and I love reading everyone's postings!