Men can be terrible but it's not that likely to encounter rapists and killers.
It is EXTREMELY likely to encounter a man who is willing to sexually assault or rape you given the chance with no consequences if you're a woman. It's ignorant of the differences in experience between being a man and being a woman to think that it's rare to encounter men who may harm you and that it's irrational to not give men the benefit of the doubt. Misogynistic rape culture is rampant, and it's very rare for men to understand that, more common is victim blaming or telling women they're irrational for being extremely cautious around every man they meet.
"Men can be terrible" is an understatement. Most women face sexual harassment on a regular basis by men who otherwise seem like normal and functioning members of society, and most women have been sexually assaulted. Just being a woman carries a massive risk on its own. Often times rape is even from people the victim knows well. Rapists don't look or act a certain way, they don't have to seem creepy, most rapists are average dudes like anyone else. There is no method to differentiate non-sexually aggressive men from the extremely common sexually aggressive men, and the extremely low risk of being caught after committing the crime makes it significantly more dangerous, because a lot of people only don't commit crimes because they know they'd face consequences.
6.5% of women reported unwanted sexual contact as their first sexual experience... On average, a girl’s forced sexual initiation was 15.6 years old.
JAMA Internal Medicine, "Association Between Forced Sexual Initiation and Health Outcomes Among US Women", 2019
When you're out in public, or at a highschool reunion, or even at a family gathering, you're likely surrounded by at least one rapist or future rapist. A meta-analysis on unreported rape, in fact, states this:
Studies of unreported rape, mainly on college samples, indicate that from 6% to 14.9% of men report acts that meet legal definitions for rape or attempted rape
Lisak, D., & Miller, P. M. (2002)
And this study from 2014 suggests that 1/3 of white college-aged men would rape a woman if there were no consequences, despite only 13.6% agreeing they would when explicitly pointing out that it's rape. Studies like this also make it obvious that a large portion of men don't think rape is rape.
Various other studies suggest a similar or higher amount of men would try to pressure a woman into having sex if she said no, including by getting her under the influence of drugs/alcohol or by attemtping to manipulate her with verbal abuse. Which, obviously, is rape.
And keep in mind, this is only the portion that voluntarily said they would. The actual number is likely higher considering that people tend to undersell "embarassing" behaviours or thoughts, like drug abuse and desire to rape, even on studies which aren't face-to-face.
That's why being alone with a random man is a much higher risk than being alone with a bear to most women.