When you get rid of something that advocates horrible things, and there's a market need for advocating horrible things, something else will fill the need anyway. Thus, it might be better to just phase out the bad parts leaving the good ones in place. Case in point: revolutions are usually not a success stories.
Or, lets talk about the split-offs. Ever talked to a Seventh-day Adventist? Do you know what keeps them going? The book of revelations is what keeps them going. Because it promises them that all their enemies will be roasted by god at some point. Pretty fucked up as the fundamental driving force in a belief-system.
My opinion still stands: All the major religions on this planet have such a broken legacy that all we can do is to get rid of them completely.