The reason men find breast feeding in public ‘disgusting’ is because it significantly increases risks to the baby being fed, and also puts the mother in a vulnerable position. It is putting a feeding child in a public sphere which is where the biggest danger to a baby is: it shows a lack of awareness and the natural reaction is revulsion.
A woman you’re seeking to breed with is seen in a different way than a woman who is breast feeding and has already been bred with. They aren’t being compared on the scale of beauty: one is based on beauty, while one is based on safety. We are literally designed to think in this way to ensure survival of the next generation. Think about it, this woman has spent nine months incubating her partner’s genetic coding and formed it into a helpless baby which needs constant protection. She then decides to take the most intimate and vulnerable moment of a baby’s life (feeding, and affectionate bonding) and to display it in the most danger prone place possible: the public sphere.
I always find it odd that men’s more noble natural inclinations are always put forward (especially by women) in a way which make them seem heartless and primitive. If for example, a father was with the breastfeeding mother the safety of the baby wouldn’t be risked and people would fail to be repulsed by it. Women are designed to react to a baby’s needs regardless of the social and environmental situation. Men are designed to react to a baby’s social and environmental situation to make it as safe as possible by posing a threat to anything which would harm it, and thus would react in a way to protect it.
A simple example is if a breast feeding woman gets attacked, she’s won’t have much of a defence.
An understanding of the way we think and why helps to grasp why we naturally react in such odd ways.
Bear in mind, I am explaining and putting forward a hypothesis for debate, not condoning.