The only person who can know their real motives... is the person itself. And sometimes not even that. Plenty of time we lie to ourselves and repeat "mantras" to apace our conscience... We delude ourselves.
I think they are brainwashed... and used their beliefs to excuse their crap.
We judge their actions from our new point of view. And they judge our actions from their point of view. In both we cases we think each other actions are despicable.... and yet at some point I myself shunned an aunt who was disfellowshipped.. I remember feeling all self-righteous..for i was doing "God's Will"