Eh, that argument works on any claim and is nonfalsifiable-ish, so I think it can be ignored.

People buying more chocolate ice cream than vanilla? Could be changing preferences or Hersheys marketing, or it could be undetected brain worms. People voting for one political party over others? Could be that party is campaigning/governing in a more popular way, could be brain worms.

If there’s evidence of contaminants or whatever influencing behavior strongly enough to change large scale demographic trends, then present it. Otherwise, your best chance at good data is to take people at their word when they say why they do things.