Is it wrong of me to think "evolution in action" here?
absence of evidence is not evidence of absence
> A study among expatriates in Nepal suggests that immunity may take up to seven years to develop—presumably in adults who avoid deliberate pathogen exposure.[18] Conversely, immunity acquired by American students while living in Mexico disappeared, in one study, as quickly as eight weeks after cessation of exposure.[19]
I suspect it's your gut flora that adapts; but it's not your DNA.
We’ve bubble-wrapped far too much of humanity, especially in western societies.
And while everyone is entitled to their own life (excepting some of the most egregious of murderers), what we are not entitled to is artificial insulation from the consequences of our actions and decisions.
Furthermore these people aren't folks who wandered by and saw a water feature fit to slake their thirst they deliberately sought it out. They are emphatically so stupid it would actually be a shame if they had kids.
Nobody actually walks around pulling off warning labels and hoping people hurt themselves. People in general do as they did here and go to extensive efforts to keep said idiots from harming themselves, then turn around and live in a society that is worse off for having the idiots.
This is why people blow of steam by saying spiteful things on the internet. This is emphatically normal.