Using makeup to enhance your looks is not comparable to starving yourself to attain a “thigh gap” that was created via Photoshop.
ETA - please don’t quote me out of context
So what you're saying is that it's okay for women to reach for an unattainable look, it's only the extent of the process you have a problem with. Who decides the limit?
Even if it does slow down one thing which i doubt, 10 more will pop up. Corsets date back to the 16th century, with the bindings so tight in some cases it took the assistance of a strong helper to tie them. Surely that couldn't have been healthy. The oriental practice of foot binding dates back a millennium and was practiced to create the idealized foot. The list goes on and on. Like prohibition in this country, people still drank, and this law will do little if anything to change feminine perceptions of the ideal image.
As to the effect on young girls you're missing what should be "the most important influence" on any child's life - the parents.