In 1918 at the height of the Spanish flu, Philly decided to NOT cancel a parade, but St. Louis did cancel their parade. In the end, over 12,000 died in Philadelphia and 700 died in St. Louis. So, stop complaining about cancellations
Source please, and without details such as cases before the parades, population age and density, crowd size, temperature, health care, and more, then your proffered correlation=causation is specious, as is this comparison with Covid-19. Yet with the Spanish flu, which unlike Covid-19, caused extensive deaths among young and fit persons, although the est. deaths have been reduced, and malnourishment, overcrowded medical camps and hospitals, and poor hygiene promoted bacterial superinfection. (https://en.wikipedia.org/wiki/Spanish_flu)
And in such a case, I support cancellations of crowed outside gatherings, besides gatherings in enclosed areas, which I noted as fostering infection, and which should be shunned in the case of Covid-19, while those quarantined need sun and fresh air each day if possible.