This comparison falls apart the moment you're talking about matters of moral, conscience, or basically anything that doesn't have an epistemologically solid answer.

People can debate these issues, arrive at different answers, and still get along at the end of the day.

When those issues are compared to math, where one side is automatically Right and the other side is automatically Wrong and you are Unreasonable if you don't agree... not so much.

A part of being a reasonable person is recognizing this and understanding that the process you went through to arrive at the opinion you hold is not even a little bit comparable to the rigor and certainty of the answer to a child's math problem. The comparison is inherently dishonest.

I've never had a job involving "moral, conscience, or basically anything that doesn't have an epistemologically solid answer" except the moral issues that were clear-cut. E.g. flat-out illegal. Nor have I ever had anyone use the word "reasonable" that way in such a discussion.

I'm the technical expert wherever I work, and yes, the situation is pretty clear-cut. The abuse of the word in such clear situations is why I used an arithmetic analogy.

"I'm the technical expert wherever I work..."

Therefore my opinions are correct and yours, to the extent that they differ, are wrong.

Some of those things do have epistemologically solid answers, but our culture of 'agreeableness' has forced people to say otherwise for centuries on end, regardless of what the truth may be.

yep. it has become a weasel word where the speaker means to say "agreeable" but knows that "reason" has more social status than "agreement" in most contexts.