Wooly, I never said breasts were no more sexual than any other body part.
My mouth, for example, has been involved in various sexual activities. I believe the mouth is widely considered an erogenous zone. It is much more sexual than many other body parts, such as elbows.
I also go on buses with my mouth blatantly visible to all and sundry, using it to talk to my children, eat food and so on.
And if some random person came up and used their mouth to lick my foot, or stuck their dick in my mouth, I would consider myself sexually assaulted, as per your example. If someone grabbed my mobile phone, another way of communicating via text rather than speech, I wouldn't consider that a sexual assault.
So all very similar to your but breasts are sexual argument.
And I don't believe that me having my mouth visible in public and not wanting any mouth related sexual assault to happen makes me a hypocrite, or that I should have to be understanding that some nutter can't handle me going around with my mouth visible.