Right, if you ignore the fact Asians make up a third of SV and hugely contribute to the tech scene, the area is totally lacking diversity.
NYC is so superficially centered on appearances, that I would never want SF to be like it. The type of strange ideas and interesting people I met in SF wouldn't have thrived in NYC. It doesn't surprise me that something like YC bloomed in SV, not in NYC, at least until it became a trendy industry. There's a reason why industries that involve appearances thrive in NYC, such as media, advertising, and fashion.
Don't get me wrong, I love NYC, I lived there for a number of years and missed it when I moved to SF. But I've always disliked the sense of superiority that NYC has over the rest of the country.
From my experience on living in both cities, NYC might be more diverse in industry, but at parties I found people in SF to be far more open to more thought provoking, controversial, and unconventional ideas.