Rugrat- In response to your original post, I understand why it may have caught you off-guard, but chances are it was not meant in any kind of offensive way.
I play softball on a team that is split about 50/50 among African American and other races. I'm one of the "other" races, but whenever one of my African American teamates shakes my hand, its with the "soul brother" handshake. I take it as a complement, that even though we may be of a different race, we are teamates and "brothers". Consequently, I could see myself using that same handshake (in an informal situation), with someone who is AA but not expecting it. My intent would not be to offend, and in fact would be the opposite.
Chances are, the character was either AA, or someone like me, who was just trying to be friendly.