Is Dimond relaying Siscoe's argument that an internal heretic is not expelled from the Body of the Church, and then arguing that it does?
The video uses incredibly sloppy language.
I listened to the a few minutes of the video and it seems that it is saying that Siscoe claims that a person who publicly proclaims heresy cannot be considered a heretic because, until he's been judged by a competent authority, the heresy is, by definition, internal.
But it also seems that the Dimonds are arguing that an internal heretic is expelled from the Body of the Church rather than arguing that when a person who publicly expresses his heresy it is no longer internal since it is, obviously, public.
Their language in this video is not precise and, quite frankly, makes their arguments against Siscoe weak. There are other written refutations of Siscoe's thesis that are precise and strong that one should not resort to these people for their arguments.