Phrasing an opinion as if it were a fact does not actually make it a fact. Something that is based on speculation and conjecture, without anything factual to support it, is actually not factual.
For example, if I state that “I think little green men live on Mars”, it is obviously an opinion. I can’t know that, there is no evidence of it. Just because I leave off the “I think” if I rephrase it as “Little green men live on Mars”, doesn’t magically transform nonsense into fact.