This is what the Watchtower teaches, so I must preface it by confirming that I am in no way endorsing their ideas.
The concept of sinning against the holy spiit is so airy fairy that the Watchtower never is able to pin point exactly what it is. The following Watchtower shows it can be done by those of the other sheep, even though they do not receive the holy spirit. It also states that the Anointed can be d/f and then reinstated, so an anointed being d/f does not mean they have sinned against the holy spirit. The article concludes:
*** w52 2/15 p. 127 Questions from Readers *** Many in Satan’s visible organization sin against the holy spirit by deliberately and willfully disobeying what they know to be written in God’s Word and by not conforming to the new world society when they see the manifest operation of God’s spirit upon his visible organization.
So the Watchtower tries to make the point that anyone that knows the WTS is Gods organization and does not follow it is sinning against the holy spirit.