Why does grim yell at gram in chapters Thirteen and fourteen of freak the mighty?

In chapters thirteen and fourteen of "Freak the Mighty," Grim yells at Gram out of frustration over their differing views on Kevin's health and the challenges he faces. Grim is deeply concerned about Kevin's condition and feels overwhelmed by the situation, leading to tension between them. His outburst reflects the stress and fear they both experience as they navigate Kevin's illness and the impact it has on their family dynamics.