Anyone who thinks the task of refuting Bahnsen's exegesis is impossible is either untrained in the discipline of exegesis or has not applied their training to an analysis of Bahnsen's work.
Anyone who calls Bahnsen's exegesis of Matt. 5:17-20 "masterful" simply has not done his homeworks and tested Bahnsen's work against sound exegetical standards. Quite aside from the question of whether his conclusions are correct, Bahnsen's methodololgy is so deeply flawed that the best one can say is that he has not made his case. He chose a novel meaning of "confirm" for "pleroo" in Matt. 5:17 without sufficient justification for doing so, and he did not mention let alone discuss two of known contemporary meanings for that word involving "completing" something or "completing" a set period of time that something would last. Competent exegetical practice requires discussing these meanings and explaining why they are to be rejected. Bahnsen repeated the mistake of insufficient justification and no discussion of a probable alternative when he gave no grounds for selecting the stronger meaning of the Greek word behind "but" in the same verse against the weaker meaning of the word. He made an additional error when he claimed that this stronger meaning of "but" forced a meaning on "pleroo" that must be the abosolut antonym of "destroy/annul". Any competent exegete would recognize that the meaning of the words setting out a contrast is not determined by the conjunction used, as Bahnsen did but is determined by the meanings of the contrasting words themselves (in this case "destroy" and "fulfill") which, in so doing set up the intended meaning of "but". Moreover Bahnsen commits other errors: he repeatedly cites various commentators as supporting points he makes, when in fact they disagree with him! and on at least one occasion in a later discussion he refuted his own argument without realizing he was doing so!
If anyone wants to see the proof of these assertions email me at email@example.com.