"There is a disturbing trend for pre-teenage girls to wear sexually provocative clothes and make-up."
Adverts selling sexually provocative clothes and make-up to children would, if they truly outraged the parents, be a terrible idea. Companies go to considerable lengths to build a positive public image and spend large amounts of time and money on corporate social responsibility and other such measures. The outraged parents have every ability to prevent their children shopping in those stores so the market would be small - restricted to those children sufficiently smarter than their parents that they can fool them - and not worth the public relations disaster.
Parents are only pestered because their will to resist their children is obviously weak - because they have no credibility that they will resist the pestering.
Parental will is weak because of relativism. Though they want the best for their children they feel guilty about placing any stricture upon their behaviour. They have spent a lifetime being told that to be judgemental is the worst kind of sin. In the adult sphere they are expected not to tolerate every moral choice but to go way beyond that bar and treat them as equal.
As a result they don't feel at all credible themselves when confronting their children and telling - for example - their nine year-old that dressing like Christina Aguilera isn't remotely appropriate. The language of 'appropriate' and 'inappropriate' feels archaic. When facing a pestering child parents who have lost the very idea of right and wrong have no answer to their claims that standing out will be inconvenient. They will choose the path of least resistance. As so many have chosen that path of least resistance being the exceptional parent becomes ever more difficult.
Increased commercialism isn't the important trend at work in the sexualisation of children or childhood obesity. Advertising is a product of the society around it and ours has a very hard time really condemning the sexualisation of children and treats those without the willpower to control their weight as victims. Laws to curb advertising are a lazy response to a serious issue and completely miss the point. They are an attempt to find a policy lever to address a problem created by cultural and intellectual change.