In terms of the allergy, I agree that it's most likely either the latex or something else that's present when they're not fully cooked. I'd also be curious as to whether either the person digging them up or the person cooking them is more likely to have an allergic reaction than the people merely eating them.
They were interesting, but I wasn't convinced. I think it's not so much racism as those plants not fitting into traditional European methods of large-scale food production (unlike e.g. potatoes, corn, peppers, tomatoes, squash &c.). If you look at the traditional cuisine of e.g. the Tidewater region (up until the 1950s), you find an amazing amount of aboriginal foods in the diet.
I think that if they could have included something in their methods of cultivation, they would have.