The only way I see is to have an objective definition, which can be objectively applied no matter which glasses I wear. What would that definition of sexism be?
No, this is silly. All language and behaviour has context. This idea that you can eliminate the shades of grey to find some absolute definition is largely what makes me uncomfortable with the more extreme proponents of this stuff. Such as those who believe particular words in isolation are always bad regardless of context.
It would be much healthier culturally if we take into full consideration the meaning and intent of the accused, as well as the feelings of the apparent victim. Which I feel like the OP's comment highlights.
For ex, the moderator could have been oblivious to the fact she hadn't spoken much, as the only woman there, and when he asked the question he may indeed have been so excited that he spoke for her. The kind of people who get moderator jobs at big events like this are the extrovert types. The ones who talk before listening... so I don't think that is entirely unrealistic here.
An extrovert too busy looking for a chance to talk himself, instead of being sensitive to the amount others have spoken? This just as likely as him believing he could do a better job at explaining the subject, merely because she was a woman.
So if we look at the objective facts: that a lone woman on a panel wasn't allowed to speak, even when her expert subject was brought up, would seem like the moderator was sexist. But digging into the context it's possible there was far more to it and this is often lost in the shades of grey when you only view it from a single perspective.
To know the truth we would need to look at how the other panel members were treated. If the moderator spoke for them as well, or tried to but was forcefully overridden, then sexism probably doesn't come into play. But if she was the only one, well... I wish I had time to view the proceedings for myself.
Fwiw, the linked post says the moderator comments on Veronika Hubeny's lack of speaking time, so he wasn't unaware. This presumably is what prompted shifting the discussion to her field. I'm not suggesting this provides any demonstrable proof the moderator was being sexist—Veronika's comments indicate her own take on the moderator's potential motivations.
Nonetheless, I do agree there are pitfalls and dangers in attempting to always distill nuance and shades of gray into stark, problematized blacks and whites. Sexism, like racism, definitely exists—it is woven into the cultural fabric and narratives that compose American society and consciousness. However, we are long past the overt institutionalization of these isms, which leaves recognizing it a regrettable slog through subtler shades of gray that leave opportunities for vehement disagreement. Sometimes I think everyone would be happier if they lived several decades ago, when these isms were black and white, and found themselves standing in solidarity on their own bridges of Selma.
Objectively, we know that many in the audience were also horrified by what they were seeing - because they verbally stated this afterwards. The moderator clearly had no explicit "intent" and the subject has also stated that she didn't detect this as "sexism". But had noone in the audience spoken out, a large portion of the audience would have come away feeling they had experienced a reminder that women are subject to routine gender-based mistreatment - even if neither person on stage saw it that way.
It's not possible to use an objective definition unless you can read minds. Use your best judgement, and keep in mind history and context. Actions don't exist in a vacuum.
Human interaction can't be reduced that way. You can't make objective rules for things that are inherently subjective. It's why we have judges to preside over court cases, rather than just follow a flow chart, for example.
The dichotomy of objective/subjective is a weak rubric for complex situations involving multiple observers and actors all of whom have asymmetric experiences. Sexism is an intersubjective phenomenon which means that it can only be analyzed effectively by taking into account many viewpoints and reconciling them.
As an example in physics of a situation where multiple observers have to be reconciled, imagine a spaceship zipping along at some fraction of c, observed by two observers, both of whom are moving some fraction of c relative to each other. Their observations of the length of the spaceship don't match up naively, but special relativity tells us how to reconcile their measurements: This allows us to consider their measurements as describing the same underlying phenomenon.
In this situation, one of the observers, A, can infer what B sees because B's measurements should only depend on properties of B that A can observe. So A can construct B's measurements by observing B, without B having to do anything. This is a very easy epistemological situation to deal with.
In a complex social situation, A can't take independent measurements and get the big picture. B needs to tell A about how they perceive the situation. Furthermore, B can't reasonably tell A everything all at once: Imagine if we had to spill all of our guts every time we wanted to reach a common understanding. Nothing would get done! So, reaching common social understanding needs to be a process, a dialogue between people.
Understanding phenomena like sexism involves communicating and interacting with each other in order to understand how we communicate and interact with each other. It's a much more complicated epistemological situation than observing an external object, like a spaceship. That's why I think you won't be able to get a satisfactory definition that you would consider objective, especially one that fits in a hacker news comment.
It would be much healthier culturally if we take into full consideration the meaning and intent of the accused, as well as the feelings of the apparent victim. Which I feel like the OP's comment highlights.
For ex, the moderator could have been oblivious to the fact she hadn't spoken much, as the only woman there, and when he asked the question he may indeed have been so excited that he spoke for her. The kind of people who get moderator jobs at big events like this are the extrovert types. The ones who talk before listening... so I don't think that is entirely unrealistic here.
An extrovert too busy looking for a chance to talk himself, instead of being sensitive to the amount others have spoken? This just as likely as him believing he could do a better job at explaining the subject, merely because she was a woman.
So if we look at the objective facts: that a lone woman on a panel wasn't allowed to speak, even when her expert subject was brought up, would seem like the moderator was sexist. But digging into the context it's possible there was far more to it and this is often lost in the shades of grey when you only view it from a single perspective.