Sorry Chris Key but no matter why you think he did this, its inexcusable. If we don't cut Yates slack for some Post Pardum Psychosis crap then his reasons too are pretty much crap. Divorce, an affair, a cult, job stress, none of it justifies killing a wife or a defenseless boy.
Hate the sin, love the sinner. You recognize a person's abusive actions for what they are, yes. But that shouldn't stop anyone from trying to understand _why_ they did what they did. And, sometimes, it's possible to condemn a person's violence(physical and non-physical) while sympathizing with their situation.
In the case of murder-suicide vs. simple murder... Automatically the two things are entirely different. Sympathy falls easier to the perpetrator of a murder-suicide simply because suicide indicates a higher level of anguish and, potentially, a realization by the murderer that he/she should be punished for what he/she has done.
