The big issue with this virus is the symptoms seem to vary so much from person to person. Unless you were to get tested some people may not even know because their symptoms are not bad. If you did feel ill but good enough to play or work you would expose all those people and it would spread even faster because of how it is able to survive on surfaces etc.
I personally don't think they should have cancelled anything but greatly restricted access to the games. The good thing is it isn't affecting the young people much so the risk is low for them to die from it but again they are potentially a carrier. It is a slippery slope and only time will tell what happens. Either way for the NBA, NCAA, President or any other organization you will be under the microscope and you are damned if you do and damned if you don't.
I told my wife last night that I predict they announce kids won't be going back to school for a few weeks. If you look back at the history of the last great Pandemic with the Spanish Flu there is evidence that showed avoiding and eliminating the large crowds did help control the spread. Not saying that the death toll will be like that but why risk it if you don't need to.