"What did you just said? Unbelievable? What makes you think that?" Elijah is now enraged at the reaction his grandson has shown him.
Elijah expected a different reaction from Kyle and Erik. That reaction of theirs is not what he wanted to see.
"Grandfather with due all respect, I now know that you have a painful past with the Colemans but don't you think that knowing the real truth about their death is the most reasonable thing to do?" Is his grandfather not using his smart mind? His grandfather is like a dumb person because of his anger.
One of the things that his grandfather often tell him is, 'Do not let your own emotion get the best of you.' Kyle always bears that sentence on his mind. But right now, Kyle is disappointed at his grandfather; Elijah is doing the opposite of what he taught Kyle.