There aren't polymers in breads or margarines, they aren't literally "plastic".
I think people use the word "plastic" = "chemicals I don't like".
What's the point of words if you change their meaning so much?
Why not say "chemicals I don't like" instead of saying "plastic".
I reckon the word "plastic" is chosen to deliver an emotional punch about "terribly scary or bad artificial things".
So then the whole point of thread isn't facts but rather Emotions.
Not about facts relevant to human health, but
about Emotions that people have about food.
And when people tap into emotions their other motive is to tap into some kind of morality judgement, not simply healthy or not healthy, but "are you a bad person (by eating) or did bad people recklessly harm you" by offering this "plastic" food.
Also the amount of "contamination" that can be tolerated and which foods are UPF is always fuzzy... some people argue that a food that was 50% salt & 50% white sugar would not be UPF so would be ok to consume lots of... That really highlights how the anti-UPF movement is just anti "foods I don't understand" rather than truly concerned about health impacts.
At least on MN, the whole anit-UPF movement is all about emotions that people want to feel about their food and the control they have over their environment, not really about health at all, is my conclusion.
Suppose I'm just getting that straight so I can try harder to ignore the UPF threads on MN in future.