look folks, plain and simple: many people like to watch movies and tv shows that reflect people that they think they resemble. this could be a shared cultural heritage, skin colour, class, political inclinations, sexual orientations, you name it. stop knocking folk (particularly black folk) if they want to see themselves reflected in what they watch. many white people don't have this same problem: why? because most movies and tv shows reflect a great diversity of white people. there are white characters of many different classes, orientations, etc. furthermore, there are just as many really dumb white-cast shows with poor acting and writing as there are entertaining and well-written all white-cast shows. they truly run the gamut. so when you hear many people of colour complain about the "whiteness" of a show, you are sometimes hearing them lament the slim pickin's of ANY type of black diversity in shows too: lots of dumb, all black-cast shows, hardly ANY well-written all-black-cast shows. these (and many other shows that feature various races) don't get the same treatment in range or complexity.
and if you think they're just whining, well, you can just do 2 things: 1) ignore them (like the networks do anyway; not like their makin' any waves or getting any shows they want anyway); OR 2) think about your own whiteness or place of privilege and how it is probably always reflected in media, so much so that you usually never really think about it at all.