I just happened to watch a video on economics today and the very question of this topic was brought up (from 01:10 to around 06:00). Here is the link in case anyone is interested: https://www.youtube.com/watch?v=qcXtYXUCOMY&t=110s
, you seem to have misunderstood this topic a little bit. I don't know how exactly you come up with these percentages for "number of possible objective matters vs abstract matters", but the importance of this phenomenom of "reasonable dissent" (i just came up with this term, don't take it as an estabilished term) is clearly present in our everyday life at all times. It is very common for people to disagree on important matters, and when this happens, it is also common for both sides to feel that they are individually holding onto the "most reasonable" or even "only reasonable" position (even thought they are probably not).
I don't think it makes much of a sense to present or contest any "absolute numbers of possible matters" that would fall into this cathegory of "abstract" matters, but since you did give examples of sentences where sound people are likely to agree due to "objectivity", let me give you some examples on things we are likely to find different opinions (all opinions being based on different rational arguments):
On congress: Should the country spend more on military? (yes, because the countries defenses are important / no, because others areas are in need of resources)
On religion: Should a person visit the church? (yes, because they need salvation / no, because they are investing time to listen to a man)
On lifestyle: Should we avoid drinking coffee? (yes, because it can affect your sleep / No, because it can give you more energy)
On a marriage: Should we have chicken or beef for dinner tonight? (Beef, because we ate chicken yesterday / Chicken, because it is cheaper and we are on a budget)
On beliefs: Do aliens exist? (Yes, because there are trillions of planets / No, because so far we have no uncontested video recording of an alien)
The aims of this topic is to discuss why people hold onto these thoughts that if reason is what has taken then to their current belief systems (or to actual conclusions based on them), then it would also follow that other belief systems (and the conclusions based on them) are necessarily "less rational".
We have some hypothesis in the table already. One of them: The human beings input varying weights to every available evidence, and that is essentially what forms their many different belief systems and the premises they hold. Thus, some form of reason is always in place even when conclusions differ (therefore the answer to the topic would be that indeed, equaly reasonable minds CAN think differently, and that thus, for most discussions on complex matters, no side can individually claim to be the only reasonable side).
If reason is related to the ability of correctly concluding something based on a set of premises (as in avoiding paralogisms and other errors of the "process of reasoning"), and if the individual sets of premises in every person do vary according to "neural network constitution" (or even a huge bank of personal life experiences alongside possible stochastic neuronal connection formation processes), then the conclusions of the individuals can indeed vary wildly from human to human while all of them are essentially equaly rational (i.e.: there is nothing wrong in their reasoning process).
The process of reasoning alone CANNOT convince every individual and form something like a "globaly rational consensus" in every matter. Arguments from other people do seem irrational to us: any conclusions drawn by another individual will have followed THEIR premises, therefore it will be in clear contradiction to a perfect reasoning based on OUR own premises, and therefore, the conclusions of others will always seem at least slightly irrational to us (even though these conclusions are completely rational to them).
To believe that an ultimate and perfect rational answer exists to all these complex problems of everyday life is to believe that there exists an ultimate and perfect set of premises. To believe you can have such answers yourself is to believe that a limited brain can actually house this set. To believe that rational consensus could be brought from such answers is to believe that all humans could also house this same particular perfect set of premises at the same time.