I always found the plastic argument in teflon vs cast iron a bit weak. Its health risks are well documented at this point. But the seasoning on a cast iron? That is polymerized fats... One might even go so far as to call it plastic. I am told the seasoning is also a carcinogen and in my experience more likely to be ingested than Teflon from a pan (getting a good seasoning that lasts on a pan can be tough!).
FWIW I shrug and use my cast iron.