DNA does not actually work that way. Think of a shop floor with a foreman high above the floor holding a megaphone. This foreman's the DNA. He can shout instructions (information) down from on high, telling the structures and proteins on the shop floor what to do. He can tell some of the enforcer-like structures to remove offending workers who are disrupting his goals, but he has no actual power. It is the workers doing all the work, and they regularly communicate between eachother.
To make the workers radically change what they are doing by injecting new DNA is very difficult. If you've ever tried to get a bunch of employees to stay in sync, it's a lot harder than just barking orders. You have to be subtle. The best leaders are the ones who listen to what the employees have to say, and help accentuate the parts of that message which fit well with where the leader wants to go.
This is the challenge. How do you make such a DNA seurum. What is the magic message the foreman can start barking to get all of the workers to suddenly stop making what they're doing, and focus on sharkfin soup and caviar. You would have to listen to what all the cells in this man's body are saying on the shop floor to determine the message for the DNA to shout.
Now you're looking for a reality-check, but there's some pretty decent escape-from-reality feel to it, so I'd like to offer an alternative. I would not call it valid science, but I think it's interesting enough that you might get people to accept the handwaving. Consider that something made this man what he is. It is most likely a combination of nature and nurture. Something isn't ideal in his DNA, and something in his environment probably upregulated that. Maybe he was dropped when he was a child, and some of the important workers in his skull stopped doing work. The body is flexible. Other workers will try to pick up the work. Eventually some may start dissiminating information across the shop floor suggesting particular ideas coming from the foreman that shouldn't be listened to.
What if your DNA serum, instead of causing all of these changes, merely unlocked the deep dark dirty parts of the man's DNA, and provided it a few hints as to subliminal messages it could use to start distorting the way the workers think. You then stand back, and find out what happens as a effect of the seurum. You don't know for sure, because you're using a very coarse tool, but you know it will do something. Then it's the workers on the shop floor that start to develop their own dark side, letting out all the bad things they may have been trying to hold onto the whole time.
Its pure pseudoscience. There's no scientific reason to believe this would happen. But having the entire essence of an evil person direct the vile and brutal transformation is far more likely than a mere serum being able to do it. There are many groups who claim the mind is capable of amazing things. Who knows, perhaps they're right.