The other day I watched season 3 episode 8 of Stargate (Demons)
POST CONTAINS SPOILERS FOR THIS EPISODE
The episode is set on a planet inhabited by people descended from Mediaeval Europeans. They are Christians, but seem to focus more on their fear of 'demons' than of God. They are being terrorised by an Unas monster which is posing as a demon but actually has a Goa'uld - an evil parasitic alien - living inside it.
Towards the end, the Unas comes threateningly towards Simon.
UNAS - Your God has abandoned you.
SIMON - My God is with me always.
Later, the canon describes what happened:
Simon…stood before it like…like David before Goliath. The demon threw him aside and then he fell.
I'm not sure what the canon - or the writer - meant by this. Possibly he's just referring to Simon's (uncharacteristic) bravery. But it seems to me that there's more to it than that.
It turns out that the Unas was not just going to attack Simon. It was dying, so the Goa'uld parasite needed a new host. And in the end it took over the canon instead.
At first I thought - well, naturally it would choose a self-serving and nasty man like the canon over Simon.
But being a nice person has never saved anyone from being taken by a Goa'uld before. Daniel's wife and brother-in-law, for example. That's what makes the Goa'uld so scary - anyone, even good guys, can have their minds taken over by them and be used for evil.
But Simon is not just a good guy. Like David, God is with him. It's not his own strength that protects him, but God's. That's what makes the difference.
At least, that's how I interpreted it.