A sinful man could die to pay the price for his own sins, but it takes a sinless man to pay the price for the sins of others. Christ had to die whether you believe in predestination or not. The real question is not whether Christ had to die, but rather whether predestination (double or single) is true.
For me, the answer is fairly simple. If we have the freedom to choose against God–the freedom to reject Christ’s offer of salvation–then God is a cosmic gambler and his will can be thwarted. I can’t believe that I have the power to thwart God. Can you imagine the creator of the universe in his throne room saying, “Oh, I really wanted to save Brian. I had a special place in heaven for him. But he turned me down flat. Sigh.”??? No way!
A friend of mine says that we have free will but that our free will has been corrupted by sin. Adam’s sin and the curse that followed it are such that we can no longer choose God. It gives us the illusion of free will, but we are actually constrained. This is what Paul meant when he wrote about us being dead in our sins. We were dead in our inability to choose God. It takes God acting in our lives through the Holy Spirit to overcome our deadness and draw us to Jesus Christ.
I do not understand predestination, but I do know that both sides of this argument have the same problem: God could save all but he doesn’t. Why doesn’t he save everyone? We aren’t going to know the answer to that this side of heaven I’m afraid.