I don't know what his reasons are and why he ticks the way he ticks.
In the West we are all influenced by Shakespeare and the individualistic illusion that we are more unique than we actually are. You can take the Stanford perison experiment, take a look at how a quiet and reserved man like Assad behaves once he becomes part of a certain social order or take Marx's (oh my God, he said the M word) line "das gesellschaftliche Sein bestimmt das Bewusstsein" (social being determines consciousness) seriously to realize that we are more shaped by external structures than our fixed or slowly-changing core of personality.
Sure, Marcus likes his daughter but Hitler liked dogs and was a vegetarian. I also like dogs and am a vegetarian. So what? Nazis could kill in the camps and then play sublime classical music in the evening. You can be a nice and caring guy with artistic sensitivities and the most cruel brute at the same time. In other words, personal stuff is overrated, we should focus on the surface actions and not the inner depths of a person who does something which is unusual, dubious or wrong. (This is also how I would "excuse" Spock. Who cares what he feels, he gets the job done and captures Khan, albeit only with the help of his significant other. The bad potential thing about Vulcan rage is not his inner psychological life but that he might one day be unable to stop it.)
This is why I would guess that Marcus is mainly an ordinary Section 31 scumbag. Like in the real world the military a*sholes in the intelligence agencies have plenty of power because they are beyond control and can do whatever they want and like all of us they are able to rationalize whatever ugly stuff they are doing with noble motives. As Dougherty would have said "It was for the Federation. It was all for the Federation." Bullsh*t, it is about power and sadism. Unless you wanna claim that killing your own people is ordinary for a "hawk".
Which isn't such a rhetorical question as hawks are extremists. The dovish position on the other hand, speak softly and carry a big stick, play tit-for-tat (be initially cooperative/friendly but punish the other when he is not) or however you wanna call it is what game theory tells us to be the best strategy for many situations and how people actually behave in reality.
The constant indoctrination from commercial trash political television might say otherwise but the truth isn't always in the middle, sometimes one position is sane and the other is insane. The mirror image of hawks would be some stupid peacenik hippies but I do not see them influencing policy in either the real world or the fictional world of Trek ... unless one wants to argue that not having enough warships in stock to deal with something like the Borg or Dominion threat qualifies as hippie behaviour.