Ladies and Gentlemen,
It has been staring us in the face for over a hundred manga chapters.
How many times has Tobi been maimed?
How many times has Tobi regenerated his body parts?
Plenty, and what else can do that very same thing?
...Zetsu.
Tobi is Madara's mind/soul INSIDE of a zetsu clone of himself.
The only thing that would possibly have Tobi on edge would be his own body desecrated by Edo Tensei.
Think about it, I don't feel like quoting the manga right now, or stating facts that point this out to be true because frankly..I'm hungover as bloody hell, but I'm tired of these Izuna/Minato(really..wtf?..Death God's belly brah)/Sage of the Six Paths(again..wtf..if Kabuto had his DNA he wouldn't have to work so hard for his secrets..he could just Edo Tensei him) type of threads.