I'm not sure people are offended by it. I'm not sure people give a great deal of thought in RL to lots of things they end up discussing on MN.
When I have seen adults eating in supermarkets whilst going round,it has registered fleetingly, in the same way I fleetingly notice an adult dropping litter, throwing their drink cans out of the car window at traffic lights, or sitting with their feet on the seats on the train. I don't go home and stress about it and after this thread finishes, probably won't give it another thought until I see someone else eating chicken in the supermarket, when again it will register briefly with me.
I guess the reason that I am interested in the thread is not the eating in the supermarket issue itself, but more the issue of social change - in the past, people would not have dreamed of starting to eat things they had not paid for, in any kind of shop - but now, some people see it as totally reasonable, despite the fact that numerous people who have worked in supermarkets confirm that the stores really don't like it happening. The thing that interests me is that increasingly there are people who are not interested in the broader social picture/consideration of others, but who are very sure they can do what they like when they like. And the justifications are interesting too - lots of people explain the giving food to children in terms of keeping them quiet in the store - well people have always had to take children shopping, nothing has changed there, but in the past they didn't feed their children going round. And they certainly didn't feed themselves, but simply waited the hour or so it took to shop.
There's something in society now that means people think they shouldn't have to wait and their children shouldn't have to wait for anything. If they want it now, they believe they should have it now, as some kind of a right. It's just interesting. Many threads on MN are interesting, more in terms of the broader picture of society that emerges, than the individual issues themselves.