In your mind, is this shorthand a function of audience expectation or something else? Also, under what circumstances would that shorthand change?

It's a function of psychological narrative. We want to know who the good guys and bad guys are in Syria. We want to know who the good guys and bad guys are in Congress. We want to know who the good guys and bad guys are on Wall Street. All of these narratives are necessarily self-serving; Alawites love their children, too.

The narrative might change in non-fiction. It still boils down to two choices: 'this is the bad guy" or "who is the bad guy."

I've been wondering why the killer would bother to have a partner, since it seemed like his sexual needs were met and fed by his "activities" and being a known homosexual with a partner doesn't seem like it would throw people off of thinking he was out seducing marines, especially given the time period.

"kink" isn't an either/or proposition. People with lovers often adore their spouses. I had a close encounter with a known NM serial killer - my mom picked him up hitch hiking and another friend - whom I met years later - almost went back to his trailer. I thought it was this guy but the MO is wrong. Either way - the guy my mom ran across had a girlfriend who helped him; the Toy Box killer was helped out by girlfriends and his daughter.