Black sheep, I quote from the Feb 15 2004 WT, page 17, para 17:
"How can we guard against being deceived by apostates? By heeding the advice from God's Word, which says: "Keep an eye on those who cause divisions and occasions for stumbling contrary to the teaching that you have learned, and avoid them" (Romans 16:17). We "avoid them" by steering clear of their reasonings - whether in person, in printed form, or on the Internet."
So from this we can see that JWs will never know what the lies, half-truths and deceptions are, since these are contained in the REASONINGS of apostates.
But how does one know to avoid an apostate reasoning before one hears it? If you've already heard the reasoning enough to tell its apostate, DOH you've missed your chance to avoid being deceived by apostates.