Jws are hard to argue with since if you argue on doctrine they will always assume they are right and you are wrong. They are accustomed to holding different views from others and will see it as interpretation rather than incorrect information. If you want to get a shot under the radar pick facts, the good news there are so many to choose from.
Russell used great pyramid as a way of calulating 1914,
End predicted by the society more than once and all failed. The light should get brighter, old light should not be extinguished by new light but it is all the time.
Malawi and Mexico
Misuse of quotations and disingenuous use of sources from fundamentalist christians presented as scientific research.
The fact that you can't question the society or doctrines without reprecussions.
To highlight a few.
You did a great job talking to the JWs in your place I would have excused myself at the first shush and told them off for being rude.