To clarify: many concepts that we today accept as part of the natural order of things would get you killed if discussed in earlier times. We don't know what things that could get you in trouble today will turn out to be facts taken for granted in future cultures, but in order for that evolution to take place, there must be a safe way to discuss unpopular (especially to the extent of being dangerous) ideas. If the people behind any great historical revolution had been unable to discuss their ideas safely, it's reasonable to assume it might never have happened.