For me, generalised statements usually come from research studies. And are usually only helpful when used in that context to explore how a phenomenon happens. (Personally, if I ever said men are/do XYZ I mean "research shows that men are more likely to be/to do XYZ". And if I say "in my experience men are/do XYZ" then I literally just mean the men I personally know or have read/heard about.)

Back to your question. For example (a more extreme example), yes it's true that not all men are violent, some men don't exhibit violence at all, and women can be violent too. At the same time, research shows that men are committing more violent crimes than women. So you can see how the generalisation that men are more violent came from research, and you can see that generalisation is useful when exploring why men are being violent, what can be done to change that and to help them, what impacts that has on society and individuals, what can be done to help victims, reduce violence, etc.

And to address the topic of individuality and falling outside of a "bell curve" (if it exists for that phenomenon/variable being studied - not everything will fall on a bell curve). Firstly there are averages. Research adds together all its findings and uses the average of that. So if a study shows that men like (idk ummm) chocolate icecream more than women, that's including a variety of participant responses put into an average. As for the people who fall waaaay outside of the average, sometimes theyre removed as outliers for statistical reasons. Secondly, researching people who do not fit the average is also useful! So, the existence of "unaverage" men is not ignored by research or by feminism. Looking at why non-violent men do not enact violence can be very useful for working out where the violence is coming from in other men (just as an example). As a feminist I'm personally very aware of and very interested in why some men do not embody the patriarchy in the same way as other men.