Interesting guy. Guess for his statement to be true, you have to go in for the Socratic thing, "To be is to do." So, in Weinberg's construct, if you do evil, you're evil, if you do good, you're good. That's a little harsh, I think. In fact, I could even argue that if you're starving, it's evil not to steal. If your child's life depends on some expensive medication you can't afford, is it "good" to let them die, or "evil" to steal what you need?
Of course, Sartre's point was, "To do is to be" -- or, and I'm taking some liberties here, existence is based on action. Each action, then, defines your existence to that extent. In that respect, a bad action is just a small component of your existence, not a defining one. So, a bad action doesn't make you all bad? OK, again, I could argue that George Bush was wrong to argue his Manichean Paranoia, that he could do evil means to reach good ends. Torturing people is evil, no matter why you do it.
Which leads me to one of my favorite quotes, by Kurt Vonnegut, who I miss deeply:
"To be is to do"--Socrates.
"To do is to be"--Jean-Paul Sartre.
"Do be do be do"--Frank Sinatra.