As a former police officer and a military veteran as well as a husband and father to a darling daughter, I've got conflicting views on this.
The reality of it is, every time I walk out my door I am "ready for war" - I don't leave the house unarmed and my attire is always such that I can "do what is needed" whenever or wherever the situation may be. Even if I am dressed up or teaching a Sunday School class I'm usually packing or having something in reach and am ready to go. I try not to attract attention to myself.
However, I think women should be able to dress reasonably and not have their attire be an excuse for them to be attacked.
However again, the reality is, we live in a dangerous world and a miniskirt could very well be the excuse some pervert psychopath needs to justify an attack or provoke one. It doesn't mean you should never wear one, but be prepared when you head out into the jungle.
Rather than the police telling women not to wear skirts, how about they tell women to protect themselves and carry concealed instead so some pervert who tries something will learn a lesson? Given that New York has a "May Issue" policy where you have to demonstrate that you have a sufficient need for a concealed carry, the fact that the police are out personally telling women that its dangerous to come out dressed in a skirt - would that qualify as sufficient need for a permit?