I think Bookworm120 hit the nail on the head (maybe without meaning to). when someone lashes out with an insult, it is almost always meant sincerely. very rarely will someone insult in an insincere way (we call that teasing). and things that are said sincerely, imprint. in a big way.
Unfortunately, many compliments are forced or broad stretches of the truth (think: “you look beautiful” (take that dress off NOW!) or “This chicken is delicious (gag)”). and when something is not sincere, its noticeable. and it wont stay with you that long a time.