If Rader killed those people, I don't think it was because he was Lutheran. I don't think it was because he's white. I don't think it was because he is straight, married, or active in the Cub Scouts. If he killed those people, I think it's because he is a sick and deranged man, broken in some dark way.
On the other hand. If he were brown-skinned; if he were Muslim; if he were divorced, or gay, or active in the liberal causes someone on the right would be standing on a box and pointing it out -- "There it is! There is the reason he did these horrible things!"
That's another reason why the right wins elections. Progressive Americans recognize that some things -- scapegoating an entire group for the actions of a single horribly sick member, included -- are just wrong.