Because you don't know what an opinion is.
"They say that windmills cause cancer" isn't an opinion. Its referencing clear and objective circumstance.
".... cause cancer". This is an objective statement. Something can, or can't cause cancer. It doesn't matter who or what believes it or has an opinion about it.
"They say..." this to is an objective statement. People have or haven't said something.
What Trump stated wasn't some vague opinion. It was an objectively based (".. cause cancer") circumstance that had no grounding in reality. The first part ("They say...") is no more opinion than the second.
Stop playing the fraud. This is why people call you a troll and move on with their life.
You play semantics, poorly, get owned, routinely, and what salient points you have when applicable are just by products of your attempts at misdirection.
No, would you Kindly shut up.