I have been robbed, ripped off by taxistas, and met rude and arrogant people, but is this not typical of any big city anywhere in the world. I have had similar experinces in Paris Amsteram Madrid to name but a few. The real big difference here is: the people try to know you, they welcome you into thier houses and genrally treat you as one of thier own.
I have two great examples: A lady whome I met through the internet, soley to learn spanish, welcomes me into her home whenever we arrive, invites us to her family Christmas and even buys presents for my wife and I.
There is a local club, where they dance not only tango but salsa meregue and folk dancing. On our first visit they did not want to let in extrajeros (they dance badly) now whenever we arrive the patron buys us drinks and welcomes us as old friends.
There are many others I could quote, but I bring them to mind whenever (rarely) I have a bad experience.