Bob appears to be evil, but in reality, he's anything but.
Bob is a villain but has rather unconvincing Pet the Dog moments.
Downplayed: Bob is usually a Nice Guy, and his good qualities are somewhat obvious to those who know him, but he has a temper, or a massive ego or other such flaws that keep him from being a clean-cut nice guy.
Bob acts like a jerk because he's been hurt in the past, and doesn't want to show his soft side because he thinks it's a sign of weakness.
Bob comes across as a jerk but he's frequently shown to have a very good reason to act angry or annoyed, particularly if he's Surrounded by Idiots.
Bob tells everyone about how he's a nice person deep down so people can give him free passes for his bad behavior.
"I don't care what he's really like inside, that doesn't give him an excuse to act like a jerk!"
Bob decides that he will straight up be a jerkass and that's that.
Discussed: "You may think he's a jerk now, but most people who act like that are merely using it as a facade because they're insecure."
Conversed: "I really wish I could be swept off my feet by the kind of dashing bad boy who you see in the movies. Oh, he'll appear rough and uncouth at first, but deep down, he's perfectly sweet."
Bob acts like a jerk because he's been hurt in the past, doesn't want to show his hidden soft side, and because of this everyone hates him and he ends up completely and utterly alone, becoming an even more hardened Jerkass as a result.
Bob acts like a jerk because he's been hurt in the past, doesn't want to show his hidden soft side, and because of this everyone hates him and he ends up completely and utterly alone, until his hidden Heart of Gold is revealed and he and the people around him learn not to judge others by their appearances.