How far is too far?

I recently saw an alarming ad on television that made me think about how far is too far. A controversial anti-smoking ad that originally ran in Australia prior to the United States calls smokers to think about not their own lives but the lives of their children before picking up a pack of cigarettes.

In the ad, the star is a four year old boy, who is shown standing alone in a crowded train station. In order to make him cry on camera and shed real tears, the executive producer did indeed let the little boy lose sight of his mother during filming.

Is it okay to traumatize a child bringing them to tears if it helps fight the war against smoking?