Reasons people defend the Watchtower
1) They dont understand cult mind control and haven't been away long enough for it to wear off.
2)They are having a hard time admitting they were completely wrong about choosing it as a religion in the first place.
3) They like to take the contrarian argument in a discussion.
4) They haven't really adopted a new belief system and it feels uncomfortable having no belief system.
In all honesty it took me years after I left before I figured out that it was a cult and was finally able to junk all the teachings. I realized they weren't god's spokesperson, but I still thought they got some things right, like trinity and hell fire.