I fly a lot, 80-100 flight per year. Not as many as some here, but still a lot. It is inevitable that an illness and a scheduled flight will correspond. I have delayed departures, even postponed whole weeks of work, because of illness. I have had change fees waived because I changed a flight due to illness. I cancelled a cruise because of an illness that would have prevented my traveling had they learned of it but it was easily hidden. (I always buy trip insurance for cruises and it paid off in this instance.)
So, bottom line, I get it. I also know that when one is away from home it is not always possible to delay a return unless at tremendous cost, both in time and cash. In 20 years of heavy travel, I have traveled ill twice, both returns.
I also understand that every time I walk into an airport that I run the risk of being with ill people and I accept that risk as one of the risks of air travel. Sometimes people have to travel while ill, or at least make the decision to do so. I can neither control their decisions nor do I think that I have the right or authority to control their decisions. I can feel they made wrong decisions or think that I would have done differently, but the bottom line is that people will do what they want or need to do.
In the absence of regulatory authority of a government agency to control travel while ill, that is the way it will be. If and when that authority presents itself, the last that I want to implement it is the TSA.