JW's are too afraid to even attempt to defend the org's teachings with anyone who appears to be Bible-savvy.
If someone has a good knowledge of the Bible and JW dogma, the JW's "apostate alarm bell" will immediately ring, prompting a question which stops the discussion, "Did you used to be a JW?"
If all else fails, they can use 2 Timothy 2:23 to save themselves from embarrassment - "Further, reject foolish and ignorant debates, knowing that they produce fights."