"Straw man" strictly speaking means something you invented, although, yes, that is likely overly strict, since you can find someone saying just about anything. But 20%? That's a substantial fraction of the relevant population!

The other thing worth noting here is that the point of a straw-man fallacy is. In a straw-man fallacy, you replace your opponent's argument with a ridiculous version, and argue against that instead of what they actually said. Or, alternatively, it's where you are arguing against some general nebulous concept, and you instantiate it as something ridiculous -- which maybe someone is actually saying! -- and use your argument against the ridiculous version as an argument against the more general concept, tarring other versions by association. (The real solution here of course is to not argue about nebulous concepts like that in the first place, it's not a useful way of arguing, but that's another matter.)

But if you're not performing either of these types of substitution, if the ridiculous position is actually out there and you're simply arguing against it as it is and not trying to use it to substitute for something else or tar something else by association... then that's not a straw man, that's just people believing ridiculous things and you having to argue against them.