It is just a theory. There's no such thing as "scientific fact". That's simply not what science is capable of, and you're showing you're anti-science by promoting those ideas.
You're also being disingenuous if you think "just a theory" isn't a phrase constructed to mislead. Your comment implies that you understand that a theory is literally the strongest model that science can give us about a topic, but saying something is "just X" implies that there is something else beyond X. So which is it? Is a theory as strong as it gets, or can science do better? If it can't do better, then never use the phrase "just a theory".
I still think it's harmful to general understanding to put any scientific knowledge on a pedestal of being unchallengeable fact. How can we know where we might be wrong? The earth is round, is it? What if that's just a slice of it in 3 dimensions and it's actually some other higher dimensional shape? Future people might laugh at our simplistic belief based on only seeing a little part of it - similar to ancients believing the Earth was flat because it was flat as far as they could see.