The thing is, perhaps there are reasonable and legitimate reasons for preferring a kitten to arrive un-neutered.
(don't y'all jump on me!) As I have rescued kittens from shelters at very young ages-8 weeks-and the shelters neutered them, one set of brothers became part of my life. Lost at 5 yrs and almost 6 years. The vet I had (then,) told me the FUS " MIGHT have something to do with it" He was way ahead of his time, I believe. I will put this link here
www.2ndchance.info/spayneuter.html by Dr. Ronald Hines. He is making television and post and media news, as a David against the Goliaths of this world. This is because of going against long-held, sometimes unscientific, views, according to him. From my sad experiences, and in my opinion, I like much of what he says--makes me think he's really on to it.
I'd like to be able to make the best decision in my own kittens' health interest, and long life.
That said, I agree it is the breeders perogative to make their own decisions, and expect the buyer to abide by that, or go elsewhere.