> thinking derivatives are legalized gambling, and being against gambling entirely, doesn't require a lack of understanding of derivatives to be against them

No, but anyone who has an introductory knowledge of derivatives and their history will know of the Onion Futures Act, which banned "the trading of futures contracts on onions" to predictable (albeit long term) effects.

Broadly speaking, the less someone knows about derivatives and the further their work is from the production of any good (versus services), the more likely they are to get upset about it.

[1] https://en.wikipedia.org/wiki/Onion_Futures_Act#cite_note-fo...