I really don’t understand the question. Adult females have breasts, breasts have nipples. So what? I can’t remember ever noticing “visible nipples” in a professional context any more than I have noticed that the other person, since she happens to be a woman, has breasts.
I’ll try to remember asking my wife, when she comes back from her business trip, what she thinks about the issue - provided she thinks about it at all.
FTR: I’m a straight European male
ETA: It’s quite another matter if I’m ogling scantily-clad women
I’m a guy, and yet I basically agree with this. If the woman’s just walking down the street or shopping at the grocery store, it’s sexy, whether intentional or a “happy accident”. If she’s working as a barmaid, I assume she’s aware of the look and is attempting to increase her tips – manipulative but still okay. If she’s on the job as a bank teller, schoolteacher, or just about any other occupation, however, it’s unprofessional and uncomfortably distracting.
I’m female. I don’t have any opinion on visible nipples as such; unless we’re actually in medias makeout, it’s not about sex, guys, it’s temperature and/or fabric friction and not something we can control.
What bugs me is guys who insist on acting like it’s deliberate, or for their personal benefit: staring, making comments, using it as an excuse to hit on the chick, etc. I don’t see why we should have to wear padded bras to protect us from having a normal involuntary autonomic nervous system reaction just so men don’t think we’re “slutty” or “unprofessional”.