Why do some women dress in an unprofessional way at work and then get mad when men stare?
Why do some men see an inappropriately dressed woman and think this frees them (some men) of their professional responsibility to behave appropriately?
Some women, too, make rather harsh judgments of their co-workers' style of dress, but it's not often that women do or say anything above the radar. While a man's stare or blatant comment is out there for all to see or hear, a woman's whispered judgment or knowing glance to another co-worker is much harder to detect. For the record, the woman's actions are just as inappropriate as gawking or a crude remark.
If anyone in the workplace is inappropriately dressed, a higher-up will eventually have something to say about that person's lack of professionalism. In the meantime (or if the higher-up doesn't take notice), you have the option of reporting your co-worker for dressing inappropriately (an understandable distraction – sexual harassment laws work for both genders) or ignoring it. You also have the option of putting yourself in the position of getting your own quality time with the boss by doing or saying something inappropriate in reaction to the inappropriately dressed co-worker.
No one is responsible for the way someone else chooses to behave or react – even with regard to a scantily clad co-worker. If one has no more control over oneself than that, then perhaps it's time for one to consider a job that requires little or no human interaction.