The whole thing was copied from some fantasy written over at 4chan
That is not completely true.
Only one part was taken from conversations on 4chan.
There were two other 'dossiers' or 'opposition research findings'. These were requested by Obama (on Hillary) and Hillary (on Obama) back during the 2012 DNC nominations.
The Shearer and GPS 'dossiers' are re-writes of a combination of those two sets of documents.
They didn' make up these things about Trump, they simply borrowed them from the illegal activities of their own party members.