Reply #: Because she was clearly motivated by Christian beliefs.

[laconicsax]

While she was probably insane and could have chosen to kill her son anyway, the simple facts are that the reasons given hinge on her beliefs.

While Loughner's motivation is unclear, his shooting rampage at a Democratic congresswoman's event is more likely to be a result of his very real extreme right-wing beliefs rather than a possible fear or dislike of Christians. Neither fear or dislike of Christians are known or supported by his being an atheist whereas his extreme right-wing ideology is known.

Try this analogy:

Person A worships Ares. Person A kills Person C and Person B kills Person D.

A says they did it because C worshiped Cronus and Ares commands that Cronus' followers be killed. B says they did it because D cheated them.

In this case, A's religious beliefs matter because they were a clear motivating factor. B's beliefs don't matter because their actions weren't motivated by religious beliefs. B may worship Ares, another god, or no god at all, but because they didn't base their actions on religious beliefs, it doesn't matter what god they worship.