I don't like Ru paul's drag race, but my sister who identifies as queer LOVES it, as does my daughter who has otherwise feminist principles and beliefs. I don't think drag as an historic form of showbiz and expression is necessarily associated with bitchiness and the "worst" feminine stereotypes - but historically mostly revolves around exaggerated, cartoonish make-up and dress.
I understand the comparison with blackface, but I think that comparison falls short when i heard many of the contestants in RU paul talk about how empowering they found drag, how it was for them the moment they found themselves, they explore their authentic selves etc. I don't think that is true for blackface- I don't think anyone doing blackface found it empowering or as a way to explore their authentic being or whatever!!
As mumsnet is fond of saying, womanhood / femininity is about much more than wearing and dress and makeup! I don't find any of the behaviours exhibited by the Ru Paul contestants, or by Ru Paul himself to be associated with traditional stereotypical femininity- eg gentle, caring, nurturing etc. If anything, the opposite- Ru paul himself is a very masculine person, and the characteristics encouraged on the show: ruthlessness, competitiveness, excellence, endurance, loudness, these are all, rightly or wrongly, associated with masculinity. None of the contestants that i have seen scream "women" to me- they are very clearly dressed up men! both in behaviours and looks.