Yeh I have read about the inconsistencies of the Catholic Church on slavery; but in principle, morals are not changed according to the social context.
Christians or not, religious or not (though usually religious), there are people who believe in absolute truth and reject moral relativism.
It seems kind of naive to claim that morality is constantly changing for everyone.
You evaded the point made, their morals have changed that was the point, and whether they claim otherwise is irrelevant.
They may believe they know what is absolutely moral and right and that it is unchangeable, but the fact of the matter, is that they have changed their minds, and that in doing so have contradicted themselves.
And of course there are people who believe there is only a one true set of morals, which has nothing to do with what we were talking about.
What we are talking about is that in spite of this they have changed overtime, as we as a society have become somewhat enlightened and less barbaric.
Basically the Catholic Church and many other religious institutions in the word are lying hypocrites on the matter. End of that argument
Now you have opened up a whole new can of worms, can there be such a thing as a 'one true set of morals'
As a believer in objective truth (something is either true or it's not e.g. it is impossible for God to exist and not exit at the same time) I would suggest that it's impossible.
Morality does not fall into the category of truth because it is a human construct. It would be like suggesting that there is a one true best movie ever made, or book ever written. Who decides this? How do you measure this? The idea is ludicrous as it is completely subjective. Everybody is an individual with different experiences colouring their perspective on everything. Thus there is no way to form a consensus.
Therefore there is no such thing as a true morality. For of course morality is constantly changing as everybody has their own view on what that morality is. Thus going back to my previous post and point, morality changes from person to person, community to community, region to region across space and time. On a side note it is well observed that individual morality changes as one ages from childhood to adulthood. I don't have the same set of morals that I did when I was 10 or 15 and would not wish to.
Now obviously this argument excludes the possibility that there is a divine set of morals that is the 'true set' of morals. If you believe that this is true then the whole argument above is irrelevant, as it would be far more prudent to debate whether this divine entity exists in the first place to create this one 'true set' of morals.
However if you believe that there is no God but still believe that there is a one true set of morals, then do please enlighten us as to what these morals are, OR perhaps write them down and create another cult to add to the very long list of cults that believe that they too, have discovered the 'one true set' of morals that we should all follow.
Now perhaps you believe that these morals exist but we just don't know them yet. If so I would refer back to my previous point that morality is a human construct.