I think that the media plays them up and inadvertantly glorifies them. The nutty folks see the pain these shootings cause and misery loves company. Just a way to strike out at something too big or amorphous to fight, like unemployment. Not scientific but just IMO.
"God and the Soldier we adore, in time of trouble but not before. When the danger's past and the wrong been righted, God is forgotten and the Soldier slighted."