God works in mysterious ways.
That's usually the response given when something is undeniably negative and a Christian is questioned as to how said negative logically fits in with an all-loving God.
In reality it's a non-answer. It's not like they're claiming they know this to be a fact; they just believe that God is all-loving because it's in The Bible. Moving with that set of logic, a Christian has little choice but to conclude that their God(who in their mind is all-loving and all-knowing) must have some bigger plan that is incomprehensible by humans. They believe this because the part about God being all-knowing and all-loving is factual to them.
Such is the case with the senseless killing of Northern Irish newlywed Michaela McAreavey, who was killed while on her honeymoon on the small Island of Maritius last Monday, January 10th.
According to reports from reputable news sources in the UK(The Guardian, The Telegraph, The Irish Times) Michaela was having tea with her new husband, John, when she decided to go back up to their hotel room to get some biscuits to go with the tea. Her room was(allegedly) being robbed by hotel employees and she walked in on them. She was strangled and left in a bathtub.
At her funeral, Bishop McAreavey(uncle to Michaela's husband John) explained how the newlyweds were truly devoted to each other. "Their lives revolved around one another; each talked endlessly about the other." He also explained how that devotion to her husband was second only to her devotion to God. "She loved the Mass and was faithful to it. She was a young woman who prayed and whose prayer was important to her."
Now here is a woman who is undeniably a devout Christian. What possible purpose could God have for allowing this couple to marry, only to tear them apart while they were still on their honeymoon? And to do it in such a horrible way! What mysterious way could God have been taking when he decided to scar a man emotionally for the rest of his life by allowing the senseless death of his new wife?
Just for the sake of argument, let's say someone can come up with a halfway legitmate reason why this horrible event could, in theory, be considered an overall good move by God. Are we to assume that this is the best way God's plan could be played out? An omniscient, omnipotent, omnibenevolent God wouldn't let a situation like this happen to his subjects. Even if I believed in this God, I could never worship him.