"And remember, this is just the first six months of life--the available studies show these sorts of effects diminishing as the child gets older."

Sure. Your area of concern seems to be the over-selling of breast-feeding in the developed world. Mine is the over-selling of infant formula in the developing world, including China, to the point of people never breastfeeding their infants. The above was a fairly cursory attempt to find a few examples of recent, post advertising ban, research on the subject.

By the way, you may not be aware of this, but the Daily Mail is a tabloid and the author of:

http://jhppl.dukejournals.org/content/32/4/595.full.pdf+html

is a professor of Women's Studies.