Vitor wants another shot at a title and Mousasi's a good fighter but is not even ranked top 10 right now in any weight class. It's understandable why Vitor doesn't want that fight. Even if he wins it doesn't do much to elevate his position but if he loses it can drop him back to the end of the line.
Put this in perspective. Mousasi hasn't fought, let alone beaten, a top 10 opponent in 3 years. These are his opponents since the "loss" to Lawal in 2010: Jake O'Brien, Tatsuya Mizuno, Keith Jardine, Hiroshi Izumi, Ovince St. Preux, Mike Kyle, and Ilir Latifi. The only exposure a good chunk of UFC fans have had to him was his fight against Latifi, in which he didn't really do anything to improve his standings.
It'd be cool if Vitor wanted the fight. I'd like to see it but I don't agree with those saying he's ducking Mousasi. If the UFC wants to set up that fight and Vitor says no then I'll criticize him for it. But preferring a higher ranked opponent is understandable considering he's 36 and doesn't have much time left to have another shot at a title.