Often the people putting down other areas aren't actually from San Francisco. There's a huge mentality in the coastal "progressive" communities that derides other ways of life, and its mostly fostered by non-natives.
It is indeed sad and shallow.
I also don't like how some San Franciscans like to put down other areas. You can have pride in your city without insulting other people and places. As someone who grew up in a poorer area, it left a very bad taste in my mouth. Most SF people are nice, but it's those other few people who ruin it for me.