The fact that Shaykh Gibril Haddad did not say anything about the authenticity of this hadith does not in any way mean that the hadith is authentic.
I was present and contributing to soc.religion.islam when those exchanges you mention were taking place, I remember them clearly, and I know Shaykh Gibril very well. I can assure you he is an extremely busy man, and does not have the time to look up the authenticity of each and every isnad that Shi'ite polemicists ever come up with. His silence on this issue does not mean anything other than his willingness to grant, for the sake of argument, that the hadith in question was sound.
What are these other historical works that you mention?