This could quickly turn into an I&P thread at this rate, but as a health professional, I am going to say that I also believe that the BSA should come out as pro-vaccination. High vaccination rates have kept these things from being an issue for a long time, but that may not be true for long. While I acknowledge that parents currently have a legal right to decide not to vaccinate, that doesn't mean that these families have a right to have their children around mine.
Summer camps, winter camps, and all sorts of other BSA activities are high risk for disease transmission of all kinds.