You get that automatically if you try to be charitable when interpreting somebody's words. More often than not, this will put you on the same page as the person you are talking to.

Actually, I think it's easier to remember it's always an opinion than to always be charitable. Maybe I really don't like a person and so it's very hard to be charitable in a given moment, but that person's statements are still their opinion and don't get to override my own experiences.

No, sometimes people are trying to state facts about the world. Those aren't opinions. Sometimes they're wrong.

Regardless what they think they are doing, they are still stating their own opinion. If we can try to interpret things in this way, even "I am stating a fact" becomes "I believe I am stating a fact."

You have erased the usefulness of the distinction between facts -- which are statements about the world that we believe to be true -- and opinions.

The burden of proof is different.

Setting the term "facts" aside for a moment, I don't perceive a difference between "statements about the world that we believe to be true" and "opinions."

When people make statements about the world that they believe to be true, all of their subsequent actions reflect that high priority belief, and disproof causes major re-evaluation of everything.

When people express opinions, they may not act subsequently in ways that are in accordance with the opinion, and may change the opinion with more or less disruption to the rest of their actions.

I used to like cottage cheese, and don't anymore. This has no major effect on anything except my consumption of cottage cheese. I believe in everyday physics so much that I consider them facts, and would have to restructure everything in my life should gravity re-adjust to being 5% stronger tomorrow.