Yeah, think of the class bully. He'll pick on everyone in the tank, but he's the first to run and hide on water change day.
Bully/chicken fish!
Seriously though, when I first got my dottyback, I went through many days of watching him pick on and attack my clownfish without mercy. Just because he could I guess. Eventually I kept moving around the live rock and confusing him, and he relented a bit. Although the clownfish is still afraid of him, she's bigger now.
I think when she gets full grown it'll be payback time in the tank.
Either that or I'll move the clownfish and the devil will get his own tank. On the positive side, he's very active. Non stop, in and out of the liverock all day, and he's wicked fast.
Like I said yesterday, if your up for it, and don't mind watching possible aggression, go for it.
Just make sure your LFS will take him back.....mine won't even sell them anymore!