Why did the Amercan's admire John Andre even though he was a spy for the British?
Because he was extremely polite and cordial and died with amazing dignity.
An eyewitness account of the last day of Major Andre can be found in the book THE AMERICAN REVOLUTION From the Commencement to the Disbanding of the American Army Given in the Form of a Daily Journal, with the Exact Dates of all the Important Events; Also, a Biographical Sketch of the Most Prominent Generals. By James Thacher, M.D., Surgeon in the American Revolutionary Army "October 2d.-- Major Andre is no more among the living. I have just witnessed his exit. It was a tragical scene of the deepest interest. During his confinement and trial, he exhibited those proud and elevated sensibilities which designate greatness and dignity of mind. Not a murmur or a sigh ever escaped him, and the civilities and attentions bestowed on him were politely acknowledged. Having left a mother and two sisters in England, he was heard to mention them in terms of the tenderest affection, and in his letter to Sir Henry Clinton, he recommended them to his particular attention. The principal guard officer, who was constantly in the room with the prisoner, relates that when the hour of execution was announced to him in the morning, he received it without emotion, and while all present were affected with silent gloom, he retained a firm countenance, with calmness and composure of mind. Observing his servant enter the room in tears, he exclaimed, "Leave me till you can show yourself more manly!" His breakfast being sent to him from the table of General Washington, which had been done every day of his confinement, he partook of it as usual, and having shaved and dressed himself, he placed his hat upon the table, and cheerfully said to the guard officers, "I am ready at any moment, gentlemen, to wait on you." The fatal hour having arrived, a large detachment of troops was paraded, and an immense concourse of people assembled; almost all our general and field officers, excepting his excellency and staff, were present on horseback; melancholy and gloom pervaded all ranks, and the scene was affectingly awful. I was so near during the solemn march to the fatal spot, as to observe every movement, and participate in every emotion which the melancholy scene was calculated to produce. Major Andre walked from the stone house, in which he had been confined, between two of our subaltern officers, arm in arm; the eyes of the immense multitude were fixed on him, who, rising superior to the fears of death, appeared as if conscious of the dignified deportment which he displayed. He betrayed no want of fortitude, but retained a complacent smile on his countenance, and politely bowed to several gentlemen whom he knew, which was respectfully returned. It was his earnest desire to be shot, as being the mode of death most conformable to the feelings of a military man, and he had indulged the hope that his request would be granted. At the moment, therefore, when suddenly he came in view of the gallows, he involuntarily started backward, and made a pause. "Why this emotion, sir?" said an officer by his side. Instantly recovering his composure, he said, "I am reconciled to my death, but I detest the mode." While waiting and standing near the gallows, I observed some degree of trepidation; placing his foot on a stone, and rolling it over and choking in his throat, as if attempting to swallow. So soon, however, as he perceived that things were in readiness, he stepped quickly into the wagon, and at this moment he appeared to shrink, but instantly elevating his head with firmness he said, "It will be but a momentary pang," and taking from his pocket two white handkerchiefs, the provost-marshal, with one, loosely pinioned his arms, and with the other, the victim, after taking off his hat and stock, bandaged his own eyes with perfect firmness, which melted the hearts and moistened the cheeks, not only of his servant, but of the throng of spectators. The rope being appended to the gallows, he slipped the noose over his head and adjusted it to his neck, without the assistance of the awkward executioner. Colonel Scammel now informed him that he had an opportunity to speak, if he desired it; he raised the handkerchief from his eyes, and said, "I pray you to bear me witness that I meet my fate like a brave man." The wagon being now removed from under him, he was suspended, and instantly expired; it proved indeed "but a momentary pang." He was dressed in his royal regimentals and boots, and his remains, in the same dress, were placed in an ordinary coffin, and interred at the foot of the gallows; and the spot was consecrated by the tears of thousands ..."