I think breast-stimulation can certainly be enjoyed as part of sexual foreplay -- and, as others have pointed out, so can other body parts. And our breasts can also be part of our overall picture that makes us sexually-attractive. As can eyes, hair, legs, necks, hands, ears, feet, toes, etcetera.
The only problem
I have with the breast-sex association, is the ways in which some people (including and especially some church people) use it to make it more difficult for mothers to freely nurse their babies
and young children whenever and wherever the children want to nurse.
And I don't know about everyone else's children -- but mine were never into having their heads draped while eating. Except that my oldest did go through a phase (between the ages of 1 1/2 and about 3) of thinking it was really fun to get up under my big t-shirts to nurse, and have me peeking down at her through the neck-opening!
And I actually did get harassed one time when dd1 was 2 and was nursing in this way -- TOTALLY COVERED by my big t-shirt. And I was thinking, why on earth would anyone complain -- we're
using a cover, LOL.
So, to me, breasts-as-erotic is a totally cool concept -- so long as no one tries to eroticize them beyond, say, lips or eyes or hands, and essentially equate breastfeeding in public with urinating, defacating, changing a tampon, or having sex in public.

And, yeah, it's fine to call it an "intimate" activity -- I certainly do see it as intimate: it's just intimate like stroking my child's face, or hugging, or saying I love you -- NOT intimate like having sex, you know?
Maybe Kathy Dettwyler has been working so hard to separate breasts from sex because she sees this as the ONLY way for Western society to get over its squeamishness with public breastfeeding, and create a more breastfeeding-friendly society.
But I say: sexual is good. Erotic is good. And eating certainly has a sensual component -- so breastfeeding does, too. But I don't know of ANY society that says people should only eat in the privacy of their own homes ... or that if they eat in a public place, they need to erect a tent around themselves to protect others from having to see it.
So, sexualize breasts all you (general you) want to sexualize them -- just don't commit the SIN of taking this cup of nourishment from innocent children, through the harrassment and victimization of their mothers.