Everyone seems concerned that when I move to LA, I'll become a terrible person?

I'm moving to LA soon...whenever I tell people I'm moving there, they all tell me to be really careful and watch my back at all times. Seriously, everyone makes it seem like LA is this wasteland of evil and debauchery. Some of my former co-workers told me not to adopt "LA values"...and when I asked what that meant, they said not to become a drug addict, engage in promiscuous , or become a materialistic, shallow and vain a$$hole. Even my grandmother told me LA has a terrible reputation, and I need to be strong in the face of all of the challenges I'll face. Either people think everyone out in LA has terrible values or it's a really dangerous city, where crime reigns supreme. Why does LA have this reputation? Is it mostly true?