I took it as a bastardization of the "return to nature" sort of movement. It's in quotes because a type of naturalism can be very positive getting in touch with nature, conservationism etc. But the fascist version is worshipping colonialist sort of "homesteading" aesthetics and the patriarchal rugged explorer type that encourages hyper individualism and anti-social behavior.

I’m assuming political/legal naturalism, as in ‘natural law’, which for right wingers is usually ‘the Bible should be law and the correctness of Christian morality is self evident’.

I think it's more the naturalist fallacy that lurks behind transphobia, anti-vax, and ableist beliefs