What were the principal virtues of the "higher" group in Gulliver's Travels?
I assume you mean the Hyoughnyms by the "higher" group. They are the only non-human group in the book, although one could also argue that the Brobingnagians are also "higher" than most.
The horses, (Hyoughnyms), are in Book 4 and have such rules as one must experience a moment of silence when one encounters another before speaking, so each has a minute to think about what exactly he/she wants to say. THis way, they are orderly, concise, polite, and to the point. No waste in this society. They exist in a world where negative does not exist--in fact, no vocabulary words express anything but the most positive aspects of life, nature, wisdom, and knowledge. Their counterparts, the Yahoos, are basically human. They look like cavemen types--muddy, filthy, full of stench. They live to eat, sleep, and have sex. They are all that is disgusting about life. Any words the Hyoughnyms have to express negative aspects of life have the word "yahoo" attached to it. Imagine Gulliver's disgust, then, when the lady Yahoos take a liking to him, and when the Hyoughnyms decide that he is, indeed a Yahoo and must leave their company.
The principle virtues of the "higher" group are friendship and benevolence, the higher group being the Houyhnhnms.