I think the difference is that PD is using her celebrity to hawk a drug and profit from it. Certainly within her rights, but it IS hypocritical. By promoting a drug treatment for her condition, she is inserting herself into the conversation. If she does not alter how she presents her food and herself along with that, she is being irresponsible. If she wasn't out there working her health condition to her benefit, I wouldn't have a strong opinion about it. But she is, so I do.
Unfortunately, by doing so, she is putting herself out there as an example to others with similar health concerns. Should they be taking an example from her. No. But she's positioning herself as a person who is dealing with it "this way." She's using her own story to speak to others to make money, but in a very controversial way. It's gonna ruffle feathers.
As the arc of history bends towards justice, it's a new, more progressive day. --Steve Benen, The Maddow Blog, 11-07-12