Why? Political rhetoric had nothing to do with loughner, but we do know it did fuller.
we actually don't know what motivated Loughner
my speculation is that he is nuts but we don't know if he wasn't also influenced by violent political rhetoric
I also don't know what motivated Fuller. He could also be nuts
As a general rule, sane people don't usually make death threats and they most certainly don't shoot up crowds of people, including children