I can't be too hard on Marston and Peter, as Ebony White is one of my favourite comic book characters and yet he's clearly a product of the same racist depiction of African-Americans. But he has a real developed character, so you can look past the dumb visual. And this visual was everywhere in popular entertainment at the time. Even the Race Papers--African-American newspapers published by African-Americans for African-Americans--had the same stereotype in their comics section. So there must have been a shared belief that this was okay with everyone and not offensive. It's just hard to believe that people with some brains couldn't see the problem with this depiction. However, anyone who tried to show a better depiction would have to get it past editors and producers that would likely veto that, because they wanted to give the audience what was expected.
As far as the bondage and discipline goes, there's nothing wrong with it in my mind. It's a philosophy that makes some sense and I don't think there was anything Marston or his wives should have been ashamed of. They were simply expressing their love in a creative fashion. And in today's culture, we should be more accepting of these alternative situations. The thing is Marston has been outed--yet there were hundreds of writers and artists in the 1940s comics doing similar b&d (and even more recently in comics)--but they don't have the excuse of a philosophy, it's there because it appeals to them and their fans. If we were to censor comics for being kinky, we would have no super-heroes left.