Fans, myself included, like to headcanon that Zoro has killed before, but he definitely hasn’t done any murders since the series began. I think just as much of Tashigi’s issue here is in her moral view of pirates as it is about gender. She thinks pirates are evil and will always kill when they can. It is a very binary, black and white viewpoint, one which is also reflected in some of the more archaic gender politics expressed by some characters.
Hey look, internalized misogyny! See, just as Tashigi has been taught pirates = bad, she thinks women = weak. That’s not just a common view in the One Piece world, but one of the leading causes of misogyny and sexism in the real world. The lower average testosterone level of women does make us physically weaker in general, but a woman can be strong just like a man can be weak. The average cat is weaker than the average dog, but don’t tell that to a lion.
Besides that binarist thinking that has Tashigi and oh-so-many “gender critical” people stuck in their ways, even if you are going solely by statistical trends, women are not just shittier than men. On average, people assigned female at birth are much better at tolerating pain, storing fat for long-term energy usage and they tend to not have a big swinging weak spot hanging between their legs. All of these are objective advantages in a fight.
Not to mention, women are usually the ones who, ya know, make babies. That’s how we get people. Men and non-binary people can have babies too, and not all women can or should do it, but we would not have a species without women.
(Unrelated in this case, but just a little addendum to remind y’all that if you also wish you were a man, you’re probably a man. I wouldn’t sign Tashigi up for testosterone and a binder right away, but it’s worth looking into for real life people.)