I think the most obvious answer is that people find urine and feces much more offensive than breastmilk. Not to mention when people urinate they urinate on something and anyone who has hung out with the homeless knows that urine smells terrible and its messy. Wading through pools of it on the sidewalk personally effects everyone on the sidewalk. But lactating women don't tend to spray milk all over the walls of buildings. Chances are if you probably never know when a woman has breastfed somewhere. Once she and the baby are done, nothing is left behind. So it does not effect anyone besides the baby and the mother. If you don't like looking at it, you don't have to stare. Plus when you're dealing with little kids and babies people are always more forgiving. When a little boy urinates in public, people chuckle. Of course the smell of little boy pee has nothing on the smell of big man pee.
The two things you stated are facts, so they can't refuted only the comparison can, which is what everyone has done several times over. I don't know what you're waiting for other than a certificate proving that breasts aren't obscene. Short of that you aren't really arguing anything.
