Why are there people, telling new comers negative things about L.A. all the time ?

Now look. Los Angeles is a very large city. It has it's bad parts and beautiful parts. there are so many nice areas, Santa Monica, Culver City, Glendale, Burbank, South Pasadena, Long Beach (some areas),Studio City,Marina Del Rey and on.. . And there are the bad areas more south and east Los Angeles. It's a big city like i said. But why are there posters in this section telling visitors to not come here, saying it's like Detroit with Sunshine (what the... heck?), Telling people it's not that great, or say things like " trust me.... CALIFORNIA SUCKS"...." i can't wait to get outa LA" why do a lot of people or "you" say things like that to new comers ?.... i think it's a very diverse great city to live in with of course some bad areas, like any Major city. Or are "you" people Los Angeles haters, who don't live here, but just don't like it because you watch to many gang movies or what ?...