one is very different from the other. I agree yelling fire in a crowded place can't be allowed - causes people to panic, because it's not possible to 'unhear' a sound.
But posting bomb-making information (or really, any information) should be allowed. This information is voluntarily consumed, so it has no danger of causing harm without a person acting on said information (in which case, it's not the information but the person acting on it that is the problem). This applies to _any_ information, not just bomb making information.