I think Dr. Sloop made several good insights and found culturally loaded artifacts, but I felt he was reluctant to make any of his own in-depth assertions on them. Many questions were put to Sloop comparing Caster to other popular and talented athletes and why they proved less controversial. I kept answering those myself in the back of my mind as they were asked. To me, the issue is choice. Caster, while arguably as muscular Serena Williams or Marion Jones chooses to comport herself in what is a more masculine manner while the other two are consistently "acting" female. Caster sports and accentuates her lean muscular figure as a man would, but Marion is seldom seen without a pony-tail and a sports bra. Granted her figure is a bit more naturally curved, or female, but she chooses not to braid her hair into tight, masculine-looking cornrows (as Caster does). Similarly, Serena (or Venus, I forget which) was just on some commercial in a fairly evocative display of her playing in a tight, short, white skirt with sweat beading off her through tight camera shots jumping across her body. Serena agreed to the commercial, because she is not uncomfortable with this portrayal.
Caster is a controversial icon because she COULD look like a woman (as the magazine Sloop showed us) but chooses not to. She could potentially adhere to what is considered pretty for her sex, but instead obscures the line of what we consider to be a physically perceived sex. I think if she were incapable of the "transformation" of sex-transferrence, this would not be an issue. A woman who is homely and also resembles a man would not be criticized because she can look no other way. While Caster may or may not fit into that category, she is expected by hegemonic culture to do the best she can in appropriating her look to fit their neat binaries of sexual appearance.