There is a good chance in 10 years we will look back and ask ourselves why the heck it took us so long to allow the genetically engineered chestnuts. There is a big difference between genetic engineering to remove a species from existence vs reversing a bad thing we did and protect a species from going extinct. Our duty is to protect nature from us, and not not intervening when we destroy it. We did this accidentally by introducing the fungus. It is therefore Our duty to protect the chestnut by any means we have to reverse the damage we did, and restore equilibrium