"A bunch of people saying that Jesus Christ will return to the Earth soon" is also falsifiable.
What does "return to Earth" mean? Does it mean physically in a human body or is mentally felt by his followers enough?
Define "soon".
The statement "Fourty years of exposure to Flouride in the drinking water will turn our children into communists." is much better defined except for the "communists" part. But we could define a "communist test". If the children exposed to forty years of Fluoride in the drinking water fail pass the "communist" test it is clearly false.
Still, within the short time of the debate you won't find any meaningful answer to these questions thus limiting their utility severely.
I believe that discussing the inevitable return of our Lord and Saviour Jesus Christ (In the next 60 years) to be a waste of time, but that's because I believe the probability of his return, and the subsequent apocalypse of unbelievers, is zero. Unfrotunately, I won't be vindicated in this belief until 2077.