Doctrine on how to deal with pastoral situations changed a long time ago at the parish level.  Amoris Latetia simply codifies what priests have been doing for decades.  Should the Pope define divorce in terms of adultery  (both as cause and  in remarriage)? Sure.  Is there a one size fits all answer? No.  Do these four former bishops have a stake in the game because their flocks are at risk? No.  They are out to pridefully embarrass the Holy Father.  He need not dignify their rudeness with a response, although he should warn Arroyo and the other NCR.