Sure it's sexist, nature is sexist in many ways. Kind of a weird thing to discuss with a friend irl though.

The thing is, people tend to take those kinds of generalized statements personally, even if they may be true, backed by statistics, and you acknowledge outliers. For example whenever the topic of violence or rape gets brought up on reddit (which purely based on statistics and backed by simple biological differences like testosterone levels has significantly more male than female perpetrators and due to physical strength tends to lead to worse injuries) a bunch of betas immediately get defensive along the lines of “not all men - I would never...“ because they think it's an accusation towards them and/or they fear that they'll be treated like potential rapists and murderers by women. Similarly women feel attacked if you say that women in general are less logical because they as an individual don't want to be seen as less logical. Maybe they're the autistic outlier with the doctorate in Math and Physics, more likely they think you just called them, as an individual, dumb and less logical than yourself.

The thing is people are not even wrong to fear that - a true generalization cannot necessarily be used to make assumptions about an individual, yet it is exactly how we function if we have nothing else to go on. So if the aspect of you that makes people put you in box X and treat you a certain way is something you can't change (like your gender, race, some aspects of your physical appearance, etc.) then chances are that you will be affectes by the negative generalizations associated with it, even if you are a complete outlier and none of them apply to you.

Doesn't make the initial statement less true but explains why people in the references group don't like it.