Ah, Aaron, even you could not withhold your pity, did you know how this man is being punished now for having made Elspeth so dependent on him! Some such thought passed through Tommy's head, but he was too brave to appeal for pity.
"If that is so," he said firmly, "I take the responsibility for it.
But I began this talk, Aaron, not to intrude my troubles on you, but hoping to lighten yours.

If I could see you smile, Aaron----" "Drop it!" cried the warper; and then, going closer to him: "You would hae seen me smile, ay, and heard me laugh, gin you had been here when Mrs.McLean came yont to read your book to me.

She fair insistit on reading the terrible noble bits to me, and she grat they were so sublime; but the sublimer they were, the mair I laughed, for I ken you, Tommy, my man, I ken you." He spoke with much vehemence, and, after all, our hero was not perfect.

He withdrew stiffly to the other room.

I think it was the use of the word Tommy that enraged him.
But in a very few minutes he scorned himself, and was possessed by a pensive wonder that one so tragically fated as he could resent an old man's gibe.