List of reasons to believe God exists?

[The Grand Nudger]

Okay, let's discuss the mechanics of reasoning to an objective moral fact. 

Sure.

Morality almost always has to do with assessing comparative value between two or more different options. Value is influences by culture. Every generation exhibits at least small changes in culture which translates into small changes in how the population assesses value.

The geometry of desert. 

That is why abortion is a great example. 200 years ago, no one made the same arguments as supporters do today. So, obviously the early 19th century and 21st century culture reflected differing views on the morality of the issue and if the claim of the existence of objective morality is to be supported, one of them was wrong. But we are to believe there is an objective moral fact-of-the-matter that can be discovered. Please walk me through how that works.

No problem.  Let's take a look at the justifications that were offered 200 years ago for why abortion was immoral and see if they report true facts?  That's really all there is to it.  Care to set your favorite Victorian objections to abortion up for consideration? We can compare them with current observations on the relevant facts of the same matter as seen today.

(reminding you again..that we are only discussing moral disagreement, and moral disagreement in no way implies or demonstrates moral subjectivity - regardless of the specific issue under consideration. It could be that both competing positions are wrong and this -still- won't demonstrate or imply moral subjectivity.)