[joshuamcginnis]

You think we discovered that slavery was always immoral? If we "discover" things which were wrong to be now right, then you are making the case for moral relativism. I would argue slavery is absolutely wrong and has always been, despite cultural acceptance.

[JoshTriplett]

How will you feel when you "discover" other things are wrong that you currently believe are right? How will you feel when others discover such things and you haven't caught up yet? How can you best avoid holding back the pace of such discovery?

It is a useful exercise to attempt to iterate some of those "discovery" processes to their logical conclusions, rather than repeatedly making "discoveries" of the same sort that all fundamentally rhyme with each other and have common underlying principles.