country music, I don't think anyone should be upset at anyone for most of this stuff. There are times where so-called "cultural appropriation" is offensive, but Bruno and Darius Rucker are not examples of it. And Debbie Harry rapping on The Rapture isn't either. those are all examples of people who loved and appreciated a form of music and so they did it. Debbie Harry, as an example, was from NY and she was heavily involved in NY underground music culture. She discovered the early emcees and fell in love with it so so rapped on a Blondie song. There's nothing offensive about that. Same is true of Rucker.
Now, Miley Cyrus using hip-hop culture to try and increase her brand (to make herself "edgy" so that she could escape the Hanna Montana image) is a little offensive. That actually feels like true "appropriation."