There is no dress code in the Bible and nothing to indicate that Biblically breasts have to be covered *at all.*
We cover our breasts in general in this culture because that is what is culturally appropriate.
However, our culture is seriously messed up when it comes to the
normalcy of breastfeeding. I refuse to be a party to that by covering
up when I nurse. I don't flash it everywhere, but I don't hide either.
Modesty is an issue of the heart and I'm not trying to seduce men when I breastfeed so that argument is irrelevant.
Being a stumbling block refers to *sinning* and encouraging someone else
to sin. Breastfeeding is not a sin so that argument is irrelevant as well.