You and I have diametrically different opinions regarding whether Rousey "should" fight Justino at catch weight. In my opinion, Justino "should" be the one who has to drop weight for the fight. Why? Because Rousey's the star, that's why. You can place whatever value judgment you like on Rousey's stardom, or whether she has earned her stardom or not, but the fact is, Rousey is a star, and Justino isn't. When you want to fight someone who is a star, then you "should" have to fight on the star's terms.
So, she was willing to fight Carano at catch weight? Cool. Apparently, she's not willing to fight Cyborg at catch weight. And, you know what? That's too damned bad for Cyborg. Bottom line is that Justino doesn't get to set policy: she simply is not a big enough star and, based on that metric, doesn't "deserve" to. Rousey has nothing to gain and nothing to prove by fighting Justino on Justino's terms. And the fact is, Rousey is going to continue to draw for the foreseeable future, whether she fights Justino or not. Justino's only hope at a big payday, on the other hand, is fighting Rousey, on Rousey's terms. And that, as the man says, is just the way it is.