The first time Dana meets Rufus, he's nothing more than a little boy who's frustrated with his mean father and spoiling mother. He has lots of ways of acting out and many of them are dangerous, like setting stuff on fire. As Rufus tells Dana at one point, "I burned the stable once […] I wanted Daddy to give me Nero—a horse I liked […] Daddy already has a lot of money. Anyway, I got mad and burned down the stable" (2.2.99). It's safe to say that Rufus has always gotten mixed messages from his parents. His mother gives him whatever he wants and his father gives him nothing he wants. That's pretty confusing for a kid, and no, the two extremes don't balance each other out. That's like saying that constant bursts of scalding hot and ice cold water will help a personal feel more normal over time.
Dana likes to think that Rufus will grow up to be a good man. But the evidence quickly shows that this probably won't be the case. After all, Dana is fighting the entire world for Rufus' soul. How can she teach him respect for black people when the entire world around him says that it's wrong to treat black people as equals? Dana knows that she has failed when she walks in on Rufus getting beaten up for trying to rape a girl named Alice. She thinks that, "If everything was as it seemed, Rufus had earned his beating and more. Maybe he had grown up to be even worse than I had feared" (4.3.5). And the answer is yes: Rufus has grown up to be worse than she feared.
By the time he's old enough to have a sex drive, Rufus starts trying to have sex with a black woman named Alice. She wants nothing to do with him, but for him the shame of being rejected by a black woman is too much to bear. After an unsuccessful attempt to rape Alice, he asks Dana to go to Alice and convince her that her entire life will be miserable unless she gives in to his demands. As he says point-blank to Dana, "Go to her. Send her to me. I'll have her whether you help or not. All I want you to do is fix it so I don't have to beat her. You're no friend of hers if you won't do that much!" (4.11.63). In other words, Rufus takes his sexual urges for granted and thinks that Alice is the one making the mistake by refusing to give in.
By the time Alice has committed suicide, Rufus clearly has some sense of how bad a guy he is. The problem is that he's so deep in denial that he'll lash out violently against anyone who tries to point out his crumminess. When Dana accuses him of killing Alice, for example, he shouts: "Damn you, Dana! Stop saying that! Stop saying I killed her" (6.3.87). Sorry to say this Rufus, but yeah, you totally killed her.
At the end of the day, Rufus' biggest problem is that he has no clue how to deal with situations where he doesn't get his own way. Even when he was young, he'd set fires when his father didn't give him what he wanted. And now that he's older and in charge of other people, he's a total infant. Just look at the way he reacts when Dana threatens to walk out of his life: "You're not leaving! […] Damn you, you're not leaving me!" (4.16.92). The guy might as well be saying, Mommy! Mommy!" And this is really the point that Octavia Butler makes about many men: they're way too immature when things don't go their way. They'll blame the world for their problems and they'll blame the people they hurt for getting hurt.
Some readers might have sympathy for Rufus after Dana kills him. But Dana and Kevin sure don't. They end the book by looking at each other and agreeing that Rufus dying was the best thing that ever happened to them. As Kevin says, "We are [sane] […] And now that the boy is dead, we have some chance of staying that way" (Epilogue.28). It would have been nice if Rufus has somehow redeemed himself in this book. But that's not how things always happen in real life. In many cases, men live their whole lives without ever learning how to stop acting like Rufus.