You've got to be kidding. There is nothing even remotely sexual about breastfeeding an infant. If you see something sexual about it, then you should probably rethink that.
Breasts were intended for feeding children, not to be playthings. The fact that we have made them into that doesn't negate or supercede their original function. There is nothing nasty going on, and I think it's pretty disgusting that someone would find it sexual and be offended. Of course, it's not appropriate to "let it all hang out", but simply nursing your child doesn't require that, as everyone with common sense recognizes.
Don't make fun of the handicapped.