You mean lies or falsehoods about the JW's I'm assuming?
That sort of thing is most likely to be about individuals and personal grievances rather than ideology and teachings. I don't know of any but I imagine it would be something like:
"All the elders in congregation X are drunkards and their wives are gossips."
I suppose you could have a statement like "Jehovah's Witnesses don't celebrate Christmas because they secretly celebrate Satan's birthday." But I've never heard anyone deliberately lying about JW beliefs. Why would you need to when their beliefs are obviously nonsense anyway?