Wa alaikum as salam brother. This isn't what is being disputed though. The author claims that his sources unanimously show that this attack indeed occured, but this is not true.
In your post you then questioned if Sayyid Fadlullah, who according to you accepts that the threat was made but not that an attack occured, is aware of these sources.
However, most of the sources are not showing anything other than what he already believes, and the few that mention an attack seem to come several centuries later.
Which credible evidence has been provided to counter Sayyid Fadlullahs position?