The purpose of Science is confirm or deny "settled science". All great discoveries destroyed conventional wisdom.
All knowledge is really a theory, but theories vary on their likely veracity.
We should therefore speak of scientific theories on a graded scale from "almost certain" theory to "highly speculative" theory.
The Sun will rise on the horizon tomorrow is an "almost certain theory". But theory that the temperature of the Earth will rise 1° in 100 years because of man-made warming activities is a "highly speculative theory".
And I think this is a good way to frame the discussion. It avoids saying "you're wrong". Instead you can, "OK, you may be correct, but you are betting on a very dark horse."
Which came first; the chicken or the egg?
“Betting on a dark horse”...would that be Mr. Ed?