This is why, when people call for government to enforce association after they are disfellowshipped or disassociate, they miss a vital point: it would work both ways.
Sometimes you want to protect your children from the dangerous influence of nutty believers, to spare them the pain of the WTS experience and to stop it being passed on to their kids.
I think some people know, but they take the easy option rather than confronting it - effectively passing on the hard choice to be made to their children and grand-children.