I FF and wouldn't have got a bottle out in a shop, I would have gone and found a more suitable place and the baby may have had to cry for a couple of minutes.
This is the problem. You are taking your experience as a ff mother and getting it wrong. I formula fed my first dc. Every 4 hours. Very easy to plan things around. However with subsequent dc I bf. Every damned 20 minutes for the first 3 months of their lives. That is the reason we have laws protecting a mother's right to breast feed anywhere. Because to not have the option would result in mother's being forced to stay home because you really can't plan around a BF baby,
I also find it very bizzare that some of you are saying she should have left the store..and then gone out and found another store 
Should she have kept wandering in to the rain until she found a "suitable" store? I mean it's ridiculous. Half the time you're being told you should feed your child in a filthy toilet, the other half you're being told where you can't feed your baby (Sports Direct is too filthy for breast feeding apparently)
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Maybe, just maybe your opinion doesn't matter? Maybe your opinion only matters if you are the one breast feeding?