I'm buying ice-cream because I don't own an ice-cream maker and haven't yet got round to borrowing one from the Library of Things to check out whether this is a bit of kit I would use regularly. I buy ice-cream from a farm shop that makes very short runs with a very limited shelf life, hence they can do it without UPF/stabilisers/emulsifiers. It's expensive and an occasional buy only. Ice cream should be an occasional, discretionary buy anyway.
All joking aside, it's the way these packet cereals, this really mucky pretend food is presented as a treat, and the parents who want to avoid giving this stuff to their children and inculcate good habits and preferences are somehow killjoys.
And as for the 'well, we're all going to die anyway' - well, yes, obvs, eyeroll. But how you get there does make a difference to your wellbeing and happiness, whether that's being able to move freely and do things like get out of a chair and walk to the shops without knee pain, not relying upon an increasing range of meds, not becoming too fat for the nice clothes you bought just last year...
I don't think anyone is pretending that the odd bit of cake/ice cream/chocolate is a problem. It's the daily consumption of refined sugar and processed food that generates health problems. Everyone knows this, it's not controversial.