how do you rationalize staying. it blows my mind.
The reasons are different for each individual. There might be as many reasons to stay as there are to leave. Why does a woman stay with her husbamd even though he beats the crap out of her every time he is drunk? Perhaps because she has been taught that standing by your man no matter what, is the only right thing to do. Perhaps she doesn't know where else to go. Perhaps she hopes against better judgment that he will quit drinking.
'Mistakes' made by the WBTS are usually turned around in such a way that the fault for such mistakes are on the member's head, not on the GB's head. When 1975 came and went, the blame was put on 'overzealous publishers'.
There is also the issue of guilt. Has anyone tried to leave without the elders taking them on a guilt trip along the paths of spiritual weakness?
Pressure. When someone leaves, they often lose their entire family. How many people are staying in (with their body, not wih their heart), because they know they will be shunned if they quit going to the meetings?
Teachings, and especially the repetition thereof, reach deep inside. If you have been taught for as long as you can remember that the WBTS is God's organization on earth, it takes more than someone telling you that 607BCE was just another insignificant day in history. Proof doesn't mean much, because you have been taught that such 'proofs' are just satan trying to lure you into hesitation. Separation from the WBTS does not always come easy.