Diversity is the fountain of life. Without it, eubacteria would still stain the oceans a uniform rust color. Diversity makes change, experimentation, adaptation and evolution possible. When ecosystems are diverse, life thrives. When human populations are diverse, culture flourishes.
Few places on earth are as diverse as the bay area. Residents brush shoulders with Ethiopians and drag queens, Muslims and hippies, quadriplegics and republicans. The bay area shows the world that diverse peoples can live together peacefully, mixing yet maintaining distinct identities. Of course, tensions arise, and communities do not interact as much as they could. Chinatown, the Mission, the Marina, and the Castro are too often separate worlds.