The argument for incompatibilism is really very simple.
1) I am not responsible for the eternal decrees of God (or the laws of nature and the condition of the universe at the big bang).
2) I am not responsible for the fact that, given the decrees of God, I sinned at 2 PM yesterday.
3) Therefore, I am not responsible for the fact that I sinned at 2 PM yesterday.
Not Responsible for A
Not Responsible for If A then B.
Therefore, Not Responsible for B.
How can I be responsible for that which is the modus ponens consequence of that for which I am not responsible.