Not a backlash, but a clarification! The laws about promotion of infant formula in the UK are to protect all mothers' and babies' choices. The choice of whether to use formula or not - which, unlike cakes and biscuits, forms the sole source of nutrition for the most vulnerable sector of the population - is one parents should be free to make, uncluttered by commercial considerations or pressures. If a mother decides to use a brand of formula, she needs to know what price it is going to be from one week to the next, to make a fully informed choice, knowing the impact on her family budget. This is why permanent discounts are not illegal, but special offers are.
Having controls over the promotion and marketing of formula milk (and the UK law doesn't go far enough IMHO) does also do something to protect a mother's choice to breastfeed. No one benefits financially (apart from the health service) if mothers breastfeed. It is in no one's commercial interests if more women breastfeed. So a little bit of control over the way formula is marketed goes a little way to preserve this important area of infant health being scrapped over by people whose agendas are to make profits for their share holders. Now, there is nothing wrong making money for your share holders, but just as we have marketing controls over alcohol, cigarettes, fireworks, videos, medicines and other items, we have them over formula milk. We are, in effect, saying there are more important things than your profits.
Please don't think that marketing makes no difference to people's choices. In the US, where there are no marketing restrictions on formula milk, the manufacturers advertise widely, give away cartons of freebies to every new mother, and generally push in a way which would look very odd to us.
I don't think it's insulting to think that mothers would be influenced by money off or special offers. Why wouldn't they be? You are assuming that everyone breastfeeds out of conviction and sticks to their decision no matter what. In this society, women need supporting for breastfeeding, as it is not necessarily easy to do.