Nope. God is not unjust. He offers the same opportunities to everyone. It's not His fault people reject the offer of eternal life. That would be the Calvinistic view of salvation. You make some mighty big jumps in assuming God is playing favorites, even though you know I reject Calvinism.
That's fine...I'm trying to figure out what you're getting at. Sometimes people say they hold to something or reject something, but when they describe it, they are using the wrong label.
So you are saying that both thieves got the same things, the same amount of Holy Spirit prompting, and they reacted differently. And according to your post:
What the thief was demonstrating in his actions on the cross is that Jesus forgives us and sanctifies us at the same time and that it is impossible to separate the two. This also demonstrates that justification does not rely on what we do, but on what Jesus did for us.
The thief that believed was demonstrating in his actions that Jesus forgives and sanctifies us. Whether it is impossible to separate the two, I'm not sure, since the forgiveness allows us entry into the body of Christ, while the sanctification could be stretched out over the whole of our lives while we are in the body of Christ.
My point, here:
And we choose whether to apply it in our minds or not (faith).
was to suggest that the salvation was equally available to both thieves. I'm not sure, but it seems that the salvation is actually going to be executed in everyone's resurrection. But we that believe in this life are "alive" in Christ, because we know we will be resurrected, so we can live the kind of life that does not result from fearing death--We will be with Jesus in Paradise--whether that death comes sooner (the thief) or later. I think that's part of that sanctification you talk about.