We saw it in Holguin on the return trip home. when I tried to tell the guy behind the counter that it was sporting equipment (free on skyservice) he said No. We got the supervisor involved, who immediately agreed that the bag of sports equipment was no charge, and pulled it off the scales, much to the dismay of the clerk.
My advise to anyone who runs into this is to hold your ground, and demand to see a supervisor. You'll either get the supervisor, or the clerk will back down if he knows he's in the wrong. If there's no supervisor behind the desk, then look for the tour rep who are always going through the lines to make sure everyone is being taken care of. They can escalate it at that point if required.