Legitimizing the sport seems to be disingenuous. While there are several nations that UFC is not sanctioned to go to, I would argue that it has pretty much won acceptance on a mainstream scale. They have done this by consistently contracting with the best fighters in the world, and allowing those fighters to determine their careers with their performance.
I think that the delegitimizing force has a lot more to do with a fighter having a win pulled after a bad PED test on every other card [Josh Barnett, Tim Sylvia, Nate Marquardt, Vitor Belfort, Stephan Bonner, Royce Gracie, Sean Sherk, Bigfoot Silva, Chris Leben, Ken Shamrock, Thiago Silva, Thiago Tavares, among many other notable fighters] rather than the #1 P4P, in the most popular weight class, having his belt after a bad test for a recreational drug.
disclaimer: I am a proponent of legalization of drugs, and dealing with them as a health issue. I do not see punitive measures as something that will encourage healthy decisions in the future.