I don't think anyone believes that the bishops equal God.  They are, however, successors to the Apostles and as such are endowed with the Apostolic teaching authority.  

The Church moral teaching concerning sexual ethics was not based on the need for lots of children to help assist with the family economy.  It has always been grounded in revealed truth.  As for overpopulation, that is a myth.  We could fit the entire population of the world in Texas.  The problem is not with over population, the problem is that some populations are too concentrated.  The problem is also with imbalance regarding food.    

Tell me--if I am a racist but help the poor and such, am I going to escape the judgement of God just because I supported social justice?   My point is that social justice is all well and good--but if  a person is not of good moral character, they aren't going to escape God's judgement.  In other words--there is more to the Christian life than being a do gooder.