First go to Oakvale weapon shop and talk to the shop owner. Then sell the weopon you want the argumentation out of. Tell him to follow you and if he does bring him down to the end of the warf and tell him to stop. Befoere he goes away give him four beers. Now run back to the shop and your weapon should be on the counter. Steel the weapon and the argumentation should be out of it.
Note: You will loose the argumentation you took out so don't do it with a health argumentation.