Grant is very cynical and more of a realist if anything. He recognizes that there's no way for Jefferson to escape his death sentence due to the fact that he's a black man in the 1940s.
Tante Lou, Miss Emma, Jefferson is dead. It is only a matter of weeks, maybe a couple of months-but he's already dead.
The assumptions that can be made already are that Grant is not a very emotional person. He's quick to accept the fact that an innocent man just got sentenced to death, and is very blunt with his aunt on how he feels about the whole situation even though she and Miss Emma are still grieving.