Similar situation here: We used to give our DD the occasional smack... mainly when she was young (3/4yo) until one day when she was about 8 she realised that many adults thought it was wrong to smack. So when DH got really angry with her one day (and she thought that he was going to smack her) she ran out the front of the house and stood on the nature strip yelling at the top of her lungs:
"YOU'RE GOING TO SMACK ME!!! DAD'S GOING TO SMACK ME!!!".
You can imagine how mortified we were. for all the neighbours to hear. Thankfully no one said anything if they heard her. I look back now and laugh but geeeze. So, I guess all parents who smack have to accept that this is a different day and age to when we were kids. These days kids learn their "rights" (justified or not) very young. I know that a well timed smack can do wonders... but now I am convinced that there has to be a better way. We haven't smacked our sons and i think it's been for the better. just my opinion. I don't judge those that smack (in a calm controlled manner) but I just had to share my story because I think it's going to be the way of the future: kids will take advantage of any opportunity they can get to regain control. Maybe it's better to remind them that they can regain control in other ways?