It seems very plausible that if event B is caused by event (perhaps conjunctive or disjunctive) A, where A contains the full set of relevant causal influences that you are praiseworthy or blameworthy for, then x is no more praiseworthy or blameworthy for B than for A. Thus, if you get drunk and this causes you, with no other causal inputs that you are praiseworthy or blameworthy for, insult or kill someone, you are no more blameworthy than you were after you got drunk. If, for instance, you were praiseworthy for getting drunk (e.g., because you falsely believed that the alcohol was a disgusting medication that you had to drink down, and so you did, with great fortitude), you are not blameworthy at all. If your blameworthiness for getting drunk was minor (for instance, because your friends forced you to drink, but you were still somewhat blameworthy for not taking enough care in the choice of your friends), your blameworthiness for the insult or killing is no greater.
The principle here holds whether or not the causation between A and B is deterministic or not. Mere event causation does not increase one's total praiseworthiness or one's total blameworthiness. (Could it decrease it? I don't know. Maybe you think that after total amnesia one is no longer praiseworthy or blameworthy for anything that happened before the amnesia. If you think this—I don't—then event causation can decrease praiseworthiness and blameworthiness.)
Since (unlike God, though it's a hard question why the case of God differs!) we all start out in an initial state we are neither praiseworthy nor blameworthy for, it follows that if event causation is all that happens, we are not praiseworthy or blameworthy for anything, which would be absurd. Hence, there is some other kind of causation, and the only plausible story about it is that it is agent causation.