Even if "illegals" or "gang bangers" or "welfare" did and could influence ratings books, the initial post was using the terminology as a pejorative towards certain groups of people, all of a minority ethnic status.
And to DanielBoone's point about "illegal aliens" (I'm assuming you mean people who have come primarily from Mexico) and gang bangers, yes you are correct in the majority of cases these groups do listen to certain language and music radio stations, the difference is that you didn't use primarily derogatory phrasing and language to describe these groups of people/listeners. Remember the old adage, "its not what you say, its how you say it?" I think it applies to this thread