WTF that talk about Shanks being Celestial Dragon and Mihawk not fighting him for that. Shanks was ready to go on war against Marines and BB at Marineford, he didn't demand Sengoku to stop that war because of his status. Doffy was a Celestial Dragon he could have fought him in terms of status.
Shanks wants to fight Mihawk, Mihawk is the one avoiding to fight. Mihawk is clearly doesn't giving a shit if Shanks is or not Celestial Dragon.