For all three of my kids I've been very relaxed about showing them sex and violence on TV. It had a bit of an odd effect on the two older ones - they found extreme violence funny (which I didn't mind because most violence in films is pretty cartoon-like), but they became very squeamish about sex.
They'd rather watch someone's brains spill out of their forehead like a floppy blancmange than see two people kissing. Right up until their late teens. Hasn't stopped them from humping like bonobo's mind you, but they do that in private. I hope.
It'll be interesting to see how this approach plays out with Loki.
Currently he's not that interested in storylines. When he was two, he'd freak out at any sign of jeopardy on TV and start screaming. But then it became clear he couldn't really tell what a sign of jeopardy actually was. Running water scared him just as much as a monster.
He still gets a little shaky when he sees a cartoon lego man running away from a grinning pumpkin - but plonk a severed head in front of him and he's as happy as Larry.
Social experimentation on your own kids eh? The easiest kind.
Back to the running machine, daddy!!!