I think your friend is a little over sensitive. It's not snarky at all. I can't think of a single logical person I know who would assume that pet homes are lesser than non-pet homes because of such a sign. There are so many people out there who have allergies, it's just good customer service to be informative.
To be honest, my husband pointed out that to people with allergies, items made in a pet-friendly location may very well not be "as worthy" as items from a pet-free location, simply because of the impairment and annoyance that allergies cause. It's just not worth the hassle.