It is especially poignant because Tessio knows his fate is sealed, and even after Tom tells him "Cant do that Sallie," Tessio asks Tom to tell Mike that he always liked him, and this was just business. Because Tessio knew the price he would pay as a traitor, he had to know his plea was in vain, because the plea to let him off the hook "for old times' sake" was a personal plea, and this execution was just business.