

Is that necessary for plastic? The name comes from the Greek for “to mould”. For me, anything that makes long chain mouldable polymers is a plastic. Milk makes Casein or Galalith plastic, PLA is commonly made of corn. There’s a ton of bamboo fabrics that are essentially nylon made from cellulose.
I tend to say something along the lines of “what’s your problem?”
Gives an opening to hear more without committing, and makes it clear it’s still THEIR problem.