I understand where you are coming from and the concern, but this is not a daily occurrence though. It's always a baseline problem certainly, but people are clinging to one major event and think it is the norm. It's not like Shanghai has simply ground to a halt and everyone has moved away.
Smog will occasionally be a big enough problem that people will choose to stay home. The same thing happens at any other park that has "weather".
Sweltering heat waves give outdoor performers heat stroke in Hong Kong (I'm sure people were incessantly talking about SARS when that was built). A hurricane will keep you away from WDW. California sliding into the Ocean any given day will keep you away from Anaheim. Japan getting hit by a tsunami will keep you out of those parks too. Way too many people smoke in DLP so there's your side of cancer with snow. You role with the challenges of a location essentially wherever you choose to build a Disney park and adjust accordingly.
The fact that every time some news about Shanghai gets brought up, within a fews posts we have a "Lol Smog" post is really irritating and disruptive to actual conversation. This is of course a greater problem of a joke that was funny once getting repeated over and over again (by many, many different posters) for years because often information is slow! But, that's another battle to deal with another time.
Agree with most of this part of your argument.
BTW, 88 degrees and humid on 2/25 here in paradise ... it's unlikely to drop below 70 tonight. The AC runs continuously making Florida Power and Light very happy. Why do people want to come to this place?