You’ve touched on plenty different subjects, but it is actually amazing that — as we are all different and our whole living experience is pretty much only personal — there can be a situation that people with similar life experiences, education, beliefs and backgrounds can end up in totally different places — with a totally different morality and/or worldviews.
Religion is a very specific subject, similar to politics — those things are going very deep and can become interwoven with ones personality even, at this point person becomes very defensive about anything different than what they already know. This is one of many our weaknesses that can be easily abused by let’s say cults.
One of the great starting points in many fields, like science or philosophy is “I am probably wrong about many things — because I am unable to know everything, let’s see what I don’t know and put it to the test”
Obviously: this is only a comment on the internet — it is a giant oversimplification.
I thought your question was
not
— so for the first one, we might and often don’t understand the same thing from the same concepts, language often might be a limiting factor too.
That’s why many fields, like in mathematics, physics or chemistry are using their own notation to simplify those concepts, then when you learn the rules of the notation there is this underlying premise that anyone with the same knowledge of those rules will read the written concept in the same way… H₂O or 2²=4
— for the second, there are nice Quine’s criticisms in which he argues that the analytic–synthetic distinction is untenable.
Summary (from wiki) of the argument: the notion of an analytic proposition requires a notion of synonymy, but establishing synonymy inevitably leads to matters of fact – synthetic propositions. Thus, there is no non-circular (and so no tenable) way to ground the notion of analytic propositions.