Cascade, on 2013-June-30, 17:16, said:
Just yesterday we bid to 4♠, on the contested auction 1♥ 1♠ 2♥ 4♠, my opponent paused after 4♠ for a considerable time after I had removed a stop card, she then passed and her partner found a double on ♠ Jx ♥ Kxxx ♦ Axxx ♣ xxx - hardly a defensive rock. If all these players get when they do not carefully avoid taking advantage of UI is the score wound back and some friendly advice then they are unlikely to change their ethics. Certainly the evidence that I see is that little has changed in this regard for years. Aside from anything else, a player who behaves in this way will not always have the score wound back and so will in the long run benefit from their unethical play. The only way to counter this benefit while the unethical play continues is to penalise frequently. Which is what seems to be required by the wording of Law 73.
Your example is very different: There was UI and the person with the UI took an active action (which is even the action that is most suggested by the UI). Your opponent cannot possibly have tried to do it right, hence a penalty is appropriate (unless your opponents don't know what UI is).
In the case of the OP, South did not take any action (which was suggested by the UI for those who understand UI laws): he passed. Passing is a very common reflex for people who don't understand UI laws when they are trying to do the right thing (but it happens to be wrong).
The difference is between trying to get it right and not succeeding (no punishment) and not trying to get it right (punishment).
Rik