Ice storm damage in Arkansas - tree fell on house

We had that big ice storm come through central Arkansas and a massive oak tree snapped and fell on our roof. The damage is extensive - basically destroyed the whole back part of the house.

Insurance sent an adjuster but theyre saying the tree was "diseased" and we should have removed it. Is that even a valid denial reason in Arkansas? The tree looked fine to us before the storm.

Looking at probably $60k in damage and freaking out.