How do Good Infernal Pact Warlocks work?

[Dr. Strangemonkey]

I'd be tempted to set up a Theological perspective that believes it is impious to presume on a dieties will by drawing on her power for your own ends, but that manipulating infernal powers for some purpose other than their own is an act of merit.

It'd be a perspective that believed in weak metaphysical evil, but I think that actually works with the infernal pact since what you're talking about isn't a god but the renegade followers of a fallen deity.

 

[Zogmo]

Obviously they're using the 'bad' magic to do good, but how and why would someone do that?

"To use Vaapad, a Jedi must allow himself to enjoy the fight; he must give himself over to the thrill of battle. The rush of winning. Vaapad is a path that leads through the penumbra of the Dark Side...This was Vaapad's ultimate test."

Mace Windu on tapping into the Dark Side with the light saber style he developed and the challenge it presented when using it.