You are also statistically less likely to be targeted by an actual criminal if you do engage them with neutral to friendly eye contact, a nod, a hello...or even a "please, may I sit here"?
As to assuming all men are a potential threat for your own safety consciousness routine? Maybe not as necessary as you think.
A favorite incident in my life started out pretty damned bad, but...I got on a packed-solid train after work late one night (an ATL Braves game just let out two stations before mine). I stood for a bit, but as a seat became available right next to me, I bent to sit in it, and got sort of shoved off from doing so by a young white male, who refused to acknowledge my existence. A young black male who witnessed this got up, offered his seat to me, and walked over to stand right in front of asshat, staring him down, while wearing a big grin. Asshat did not look up, but got redder and redder and nervous acting, then jumped up quickly to get off at the next stop (probably not his intended one).
There is safety in numbers. At least still here in the States and other first world countries. I say that qualifier, because yeah, India and other locales of horrific savage incidents in the news lately. Kinda don't see that happening here anytime soon, though.
As to women needing to always consider where and when to walk to be reasonably safe? Of course! That is common sense. And you know that men do the exact same thinking, unless they are clueless egotists. A gun or knife, or just the element of surprise, will trump any man's physical strength, and guys know that. They might take a risk now and then, but men are crime victims as often, or more often, than women, and a long walk down a dark alley in a sketchy neighborhood is nerve wrecking for a man, too.