Literally: "And if the blind lead the blind, both will fall into the pit." [Matthew 15:14] This false soteriology continuing amongst these groups has everything to do with what their predecessors erroneously believed. The Archbishop believed this heresy, so all of his sacerdotal progeny believe it, even those who broke away from the Society.
It's difficult to even attempt to excuse these men because they should have known the true teaching to begin with...what a mess. God help them and God help us. 
I think the problem with not only +ABL, but pretty much all of the clergy and hierarchy since at least the 1940s has everything to do with what they did to Fr. Feeney. To this day he is still slandered as an evil villain and an excommunicated heretic - even by trads whenever a BOD or EENS comes up.
Aside from slandering Fr. Feeney as an excommunicated heretic for preaching the dogma, his own Church superiors in conjunction with the Jєω media, managed to convince most of the faithful in the whole world that a) it is the sin of heresy to take the dogma literally, b) that there certainly is a BOD, and that c) salvation outside of the Church is not only possible, it's so probable that it's all but a given - and Fr. Feeney is evil because he is the one who tried to take this all away.