as far as this
then you should shift away from abortion or at least mix it up with other issues. Why? Well, it functions as a kind of cherry picking. I believe Von River went down this line with you, so I am not optimistic, but the basic point is you are generalizing that we cannot reach such conclusions because we have not reached it around abortion. Foot binding however seems to be a cultural pattern that has moved from being moral to immoral, and I while certain groups have moved from thinking it was OK to not, none have moved in the other direction. WE can see similar process with cliterodectomies. The arguments against are winning against those for and people from traditional religions, modern scientific perspectives and from other paradigms are more and more coming out against it. We see groups moving away and likely cultures doing that, and I think it is pretty unlikely that any modern society will move back to cliterodectomies and other FGM. IOW it will meet you criteria.
Understand, even if some issues are resistant (potentially merely so far) to meeting the criteria you put forward, there are many that are not resistant.
If some morals do meet your criteria, then there is a weakness in your dasein based position, even if some do not (yet).
I feel I have to repeat that this does not mean that the conclusion that footbinding is wrong is objectively correct, but as an example it meets your criteria.
I think Von River used the example of forks in the eye of children, but I am trying to pick issues more parallel to abortion and more common.
It should also be pointed out that the word ‘rational’ is stacking the deck, since this is not an empirically testable adjective.
I also think it is a healthier issue to see if you can be convinced rather than if anyone who MIGHT be considered rational is convinced, unless you do not want to have a position on something.
Chattel slavery like that in the US -and certainly where there is not extreme scarcity so that what the chattel slavery is doing is moving people from being haves to having even more, rather than somehow merely helping them get by - is another example where societies are not moving backwards towards, but are moving away and it could be argued meets your criteria.
Adults having sex with children is another one. Certainly coerced sex with children.
Human sacrifice and torture as entertainment.
Some things die out and consensus is reached even cross culturally.
All of my examples happen, still, but the moral authority and legal support is disappearing or gone.
And really, because it is rather important, this does not mean that we or Iam know objectively how to live morally even around these issues, but since your definition of objective seems to be more consensus, it should work for you.