My guess is they live in the US and they're making their argument under the assumption that the treatment will be enormously expensive and you will have to pay out of pocket for it. In that case you're caught between a rock and a hard place: will I die a slow and painful death due to genetical disease X, or do I go bankrupt paying for it.

In many countries this is a genuine concern I guess. Even in multiple European countries with great healthcare and (nearly) free health insurance, "novel" (and often very expensive) treatments are not always covered.