What’s Up With the Ending?

I looked back at the brick building of the Historical Society, itself a converted early mansion. "If we told anyone else about this, anyone at all, they wouldn't think we were so sane."
"We are," he said. "And now that the boy is dead, we have some chance of staying that way."
(Epilogue.27-28)

The end of this book basically tells us that neither Kevin nor Dana (nor the book, really) feels remorse over the fact that Dana has murdered Rufus. There have been many times when Octavia Butler or Dana have tried to build our sympathy for Rufus. But at the end of the day the message seems to be, "Hey, this dude had a bunch of chances to do the right things and be a better person. But he didn't take them, so he had to die." Now Kevin and Dana just want to rebuild their lives and try to move past Rufus and the world he represented. But that's just the thing, folks. Can America and its people ever move beyond slavery? Can they ever forget that their country's wealth and power in the world is based massively on hundreds of years of slave labor? These are the kinds of questions Octavia Butler wants you to ask.