Why do we keep looking for differences?

Differences can be cool - different foods, languages, music. But we really seem to spend a lot of time thinking of ways in which people who are different from us are somehow lesser. Gays are different and therefore bad. Or migrant workers. Or folks from "foreign" places. Or folks who worship differently. Or people with disabilities. We spend an awful lot of time looking for ways that we're superior. Is it because we're afraid that someone picking something else (not that one picks the color of their skin or their sexual orientation or lots of other stuff) somehow makes the thing we "are" (or we "picked") somehow lesser? Are we that afraid that we've chosen wrong that we have to put down any choice that isn't ours ("gosh, how can folks like ____ ? with "____" being any number of things: Medieval architecture, math, tapioca pudding, a different way to worship - or not worshiping at all. Why can't we move on to the fact that I like spicy food and you don't and that's o.k.? Or I love women and you love men or you love men and women? As long as it's a choice - a real choice - for whoever's involved, it's really not my business. besides, I might discover something interesting (tapioca pudding for instance!) if I stopped judging and started just experiencing.