I'd remind them about all the JW's who have died...confused...not understanding what their Watchtower trained, re-trained & re-trained consciences required of them.
For instance, when my JW mom died needing a blood transfusion, she had no idea the WT had changed their minds again. Hemoglobin, that makes up 97% of a red blood cell was now OK'd by the WT as a "conscience matter." She did not have to die.
Maybe you can educate them on these "allowed fractions" and stress the positive..."So, if ya' don't wanna die..."
*sigh* I hate this religion.
Edited to add: If any current JW reading this believes they are in 'safe hands', if the Elite Hospital Liason Comm. is there to guide them through all the confusing medical terms...don't bet your life on it. The HLC was there...and they killed my mom. Through malice, arrogance or ignorance...she's still dead and hemoglobin was available to prevent her smothering to death.