My RD would chase the cats as they walked in front of the tank. He also had a pet rock that i wasn't allowed to touch during water changes. Great great fish and absolutley the meanest fish i have ever kept.
They are very sensitive fish..even though they are killers and agressive they have to feel comfortable in their surroundings.. i have seen the most agreesive RD's turn into pussy cats when you change their tank.. so i would say the true personality is in there ... he is just not comfortable yet.. give him time!!
Mine was a glass banger from day one. That was the the most destructive fish I ever owned. He was absolutely insane...had to let him go because at the time I didn't have a tank for just him.
try changing the set up of the tank a little bit into a way which makes the fish more comfortable. Every fish has a different personality, so you just have to feel it out a little bit.
gl