You wrote "No, the point is that the author selectively presents information that bolsters the point she wants to make." and then claim the author supports your point?

At best you are supporting hers.

She made the case for the query 'black girls' and to pre-empt comments such as yours bolstered her argument by extending it to a general case. So in no way did she 'selective present information to bolster her point', she was as even handed as she could have been (but apparently not even handed enough for some).