Maybe there's a black american or southern way of speaking for black people which I still don't buy. And no that statement held no shade or condescension in it.
You speak the way the people in your surroundings speak. If you grew up around hood people you'll likely sound like a hood person. If you grew up around country people you'll likely sound country. if you grew up around people with french accents, you'll likely sound like that.
Most black women tend to have deeper voices than their white counter parts, or at least in my experience.
One of my best friends sound like a 8 year old girl. You can't tell whether she's black or white.
Yes, there are some people who you can tell off the bat are black or white, but there are many you can hence why I don't believe there is a black accent.