Does anyone have evidence that he logged onto the character AFTER the fight started, or with the intent to use it solely in that fight against the Mollys?
This is something people aren't paying attention to. You're complaining about what he did instead of why he did it. I'd expect any Keeper in any fight between any two parties to always side with the weak team rather than the strong one, unless it's with AI, Wilde, or OC. So he acted just as a Keeper normally would act.
He was also on that character prior to learning about said fight.
Stop complaining and play the game. A single Voidrunner didn't ruin the fight.