An unproductive conversation, becoming more hostile, can hurt the HN community. This is supposed to be a place for reasoned conversation. It's already difficult to maintain that. A raging flamewar won't help in that direction.
To try to shed a little light on this phenomenon, the "it" you refer to expands to "why women and minorities may be biologically less qualified for this job, and those that are here as our teammates are illegitimate in some way."
Using the expansion in your paragraph:
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I don't understand the attempts at shutting down conversation about why women and minorities may be biologically less qualified for this job, and those that are here as our teammates are illegitimate in some way. If you think he's wrong, you share your opinion and persuade others. You don't shut down the conversation and pretend that women and minorities are biologically as qualified for this job, or that their hires are as legitimate as anyone else's.
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That's what some people are hearing. Hopefully it's obvious why management at most companies would consider these discussions to be less than helpful in fostering the most productive work environment.
Accepting your characterization here for the sake of argument: if his claims are so laughably ridiculous as to be easily refutable, people should just have pointed to studies refuting it (of which there are plenty) and gone about their day. When you can't bring up a topic in a respectful way without being shouted down, it's a bad situation.
Remember: this guy lost a job. Discriminations kill and ruin the lives of millions routinely.
http://quillette.com/2017/08/07/google-memo-four-scientists-...
If you read the memo, he is completely against discrimination, including positive discrimination.
Please show me the other well informed people that claim the opposite.
https://freethoughtblogs.com/pharyngula/2017/08/06/what-diff...
This generally happens when ideas presented in the conversation are radical and dangerous to a point the target people in the discussion feel an existential threat.
Look at the nature of this discussion. Presented in its simplest form, its a case for a merit based system. The socialist types don't like this, the very fact that merit is being discussed implies their entitlement to free resources at the expense of other hard working people is threatened. They can't allow it to go on.
You don't want people to start thinking about it.
As I look up and see this article flagged on HN (since unflagged).
The points and ideas from his memo may be wrong or they may be right (or anywhere in between) but more important than this incident has been the reaction to it. I don't understand the attempts at shutting down conversation about it. If you think he's wrong, you share your opinion and persuade others. You don't shut down the conversation and pretend the issues don't exist.