Maybe where we disagree is that I believe a change in the rule can change a person's ethical code.Secondly, if a person believes it's not their responsibility to call a foul on themselves, a rule isn't going to change that. Since the rule is not enforceable, they are still free to act on behalf of their own moral/ethical code, and use that a means of justification.
In my experience, most people who foul and just sit down without saying anything do so because they say the opponent has to pay attention, and if they fail to do so it's their loss. I don't believe they see themselves as cheating (most of them), that's just how they understand the rules and etiquette. But I believe that if the rule was changed, over time people would internalize the new approach.