How mad would you be if someone let their sick child around your baby?

[Kckckc]

Please NO rude comments!
Can someone please explain to me why people do things like this?
I understand it's none of my business but it does partially involve me and I can't help but to feel irritated. My 6 year old Step son was diagnosed with the Flu two days after leaving my house. I had a play date scheduled for My daughter who is 16 months old with one of her little friends who is under a year old but I canceled it to make sure my daughter wasn't infected with the FLU because I didn't want to get her little baby sick and I thought she would appreciate that but when she checked my message on facebook she ignored it and when she did reply back she didn't say thank you or anything of being appreciative. Next thing I know the biological mom who ALSO has the FLU as well as the 6 year old with the FLU, just called his father today saying he needed to go back to the doctor because he keeps getting a fever will now be baby sitting that little baby girl of my friends this weekend. Plus she is also sending her sick son to a birthday party. It says that a person can be contagious up to two weeks at the most with the Flu and can even pass on the virus before they even have any symptoms of their own. That is why I canceled the play date because I wanted to be sure I wouldn't affect anyone's kids especially a little baby. How miserable would everyone be if they got sick because I let my child who had the flu around them ( if she had it ) I don't understand this situation would someone please explain why people do this and Please Do not be rude I am honestly trying to grasp the concept of this because it seems totally careless to me.
I am not usually concerned with colds and other sickness but when it comes to the FLU or any kind of diarrhea or vomiting symptoms yes, I get serious. I wouldn't want my baby to feel like because I let a child with the FLU around her. She would be miserable and it's heartbreaking and Yes I know I know, Kids get sick, it happens but your suposed to TRY to prevent it