I see nothing at all wrong with selling a bunch of engines through an "online big box". If it spreads the magic what is the harm?
Let's face the facts. As electrics take over from small glow engines there's more and more Cox and other small engines for those of us that still love these things for their qualities. And if selling a "few" through Hobby King spreads the magic out to a few more folks then I can't see anything that makes this at all a bad thing.