John Thorpe is not very nice in other ways. E.g. his first conversation with Catherine includes:

Her companion’s discourse now sunk from its hitherto animated pitch to nothing more than a short decisive sentence of praise or condemnation on the face of every woman they met...

Or his treatment of his mother and sisters:
as they met Mrs. Thorpe, who had descried them from above, in the passage. “Ah, Mother! How do you do?” said he, giving her a hearty shake of the hand. “Where did you get that quiz of a hat? It makes you look like an old witch. Here is Morland and I come to stay a few days with you, so you must look out for a couple of good beds somewhere near.” And this address seemed to satisfy all the fondest wishes of the mother’s heart, for she received him with the most delighted and exulting affection. On his two younger sisters he then bestowed an equal portion of his fraternal tenderness, for he asked each of them how they did, and observed that they both looked very ugly.

And of course I am sure anyone in a JA novel who says:
“Udolpho! Oh, Lord! Not I; I never read novels; I have something else to do.” is a villain of the blackest heart. :)