Yes, I agree with Kathy Dettwyler, this is a very hard concept to get across.
 My family is a perfect example of nothing being a guarantee.  Even though my
daughter was breastfed for 2 1/2 years, exclusively for the first 5 months,
she still got diabetes at age 10.  This does not mean I didn't "really"
breastfeed totally.  It just means other factors were stronger.  And even
though I breastfed a total of around 7 years, I still got breast cancer.
 This doesn't mean I didn't "really" breastfeed totally.  Nor does it mean
that breastfeeding doesn't convey protection against diabetes or breast
cancer.  Just that it's not a 100% guarantee.

I get so tired of hearing people say, "Well, my sister's baby was breastfed
and she got sick a lot, so therefore breastfeeding really can't protect
babies all that much", etc.      Miriam