Being a parent involves a tad bit more than having fun. Of course you don't expect a deadly disease but you also do not anticipate a deadly car accident on your way to the amusement park but it could happen so it is wise to engage all safety measures including wearing seat belts. Disney's cleaning protocol had nothing to do with the measles outbreak.
JMO
I do agree with that. They can clean the park all they want, but if someone walks through the gates infected with a disease which is spread via the airborne route, well, a clean park is no match for that.