Forgiveness is a funny thing, sometimes I think it's how you are wired and has very little to do with what faith teaches you. I remember being 8 years old at CCD (aka Catholic "Sunday school") and reading about a man who forgave the murderer of his son. No one else in my class could understand why the man had done such a thing and they all stated they would never forgive someone who murdered someone they love.
But what I remember thinking is of course you forgive the person who murdered your son! Of course you do! To me there wasn't another choice. Even from that young age I knew not forgiving meant carrying around anger, hate, and resentment, and I knew one cannot do good in the world if the carry around that kind of weight.
But I also remember being very very much in the minority at my tender age of 8.
I have known plenty of Christians in my life, and despite the teachings of the church, it never seems to be a direct result of faith that makes someone capable of forgiveness or not....in my experience it's often more about who the person is rather then what church teaches them on wether they carry forgiveness in their heart or not.
That said, when it comes to the Ramseys,who's moral compass I have some doubts about....id be inclined to believe they are not the type to forgive a stranger.