To clarify my point, when I say that the game manipulates you into thinking like a psychopath like Agent 47, I don't mean that as a negative criticism of the game.
Hitman: Blood Money is trying to convey a certain experience to the player. That is, it is trying to make players feel like they are Agent 47, an extremely capable assassin who is able to think, plan, and execute a hit. He's not against killing anyone, and will always find a way.
If they want to place you into that kind of headspace, they must then therefore make the player feel that they are okay with killing any one person in the level if it means making the job easier (or even if it doesn't, as is often the case). People don't tend to want to kill others whom they identify with. The targets, or even the random guards and civilians inhabiting the level, can't be characterized in any way that would engender sympathy. Otherwise, some of us would have issues with killing them, and call afoul of the morality of their actions.
However, if they are given personality traits and backstories that are more disagreeable, then we can distance ourselves from them emotionally. This makes all of them much easier to kill in this little sandbox. Make no mistake, the assassinations are about as moral reprehensible as that the guy from Hatred. The difference being is the killing in Hatred was just done for controversy in schlock. Here, the act of killing is the almost secondary. The true thrill lies in the formulation of the plan, and experimenting with the game's mechanics as you form that plan.
The actual kill is little more than the punchline to a well set-up joke. So while the game dehumanizes the population to make it easier to kill, the killing isn't the point. That's why so many of the possible assassinations are grandiose in their scope, or provide provide some amusement in their absurdity. It's not so much an assassination as much as it is the payoff to an elaborate and well-executed Rube Goldberg machine, as a reward for thoughtful and bold play.
I'm sure someone smarter than I has made a point similar to this, but it bears repeating nonetheless.