Cor this has moved on a bit since last night! I think it's fine to eat something pre-packaged on the way round that you have every intention of paying for. Actually, although ds now knows how to behave (more or less) in supermarkets, whatever it takes to get round in one piece I reckon. So I don't think it's the end of the world if someone eats the odd grape in a supermarket.
Read a big report on retailers a while back and this is a subject that interests me - custardo, imo, your DH is pretty much right! They do exercise a near monopoly and we should, in an ideal world, be buying from small local producers/grocers. Ho hum. The profits the retailers make at the expense of suppliers and consumers is unbelievable. Not saying that justifies anything but actually, if they want parents to shop without tantrums; supply a creche, do home delivery EVERYWHERE (they don't in my area), move tempting displays away from checkouts, help with packing if you have kids with you, in fact, agree to pack it and bring it to your car with a till swipe machine, get rid of queues, pay their staff proper wages so they're better motivated and happier, etc etc etc. But don't put patronising leaflets in store because I for one, do not want to know!
About a year ago my ds threw a wobbly as I got to the checkout (with a huge trolley) and screamed at me that he wanted a creme egg as they were in a big bin right at the till. I said no as his behaviour was awful and I wasn't giving in to a tantrum. He grabbed one, started to try to open it (not very successfully) so I took it from him and put it back. The supercilious cow of an operator said "he's damaged that, I assume you'll want to pay for it?" so, like an idiot, I did. I then asked her to throw it in her bin for me as no way was ds getting it at this point. I look back and think NO! WHY DID YOU HAVE THAT BIN THERE AT TODDLER HEIGHT? If you want me to pay for this £200 worth of shopping you can bloody well let a creme egg go by and give me some help packing or some sympathy YOU COW!!!! It was an ugly day...