> why I could easily tell that the author of the manifesto is both ignorant and uninterested in the subject
Continuing to attack the credibility of a largely factual statement (the memo in question) is still not compelling. If there was evidence supporting opposing viewpoints, even hypothetically, you might want to lead with that in your interactions. Good luck with whatever you believe.
I am not attacking the cited papers, just their relevance. He might as well have said, "we should not fight global warming because of special relativity". Special relativity may be true, but if you think it relates to global warming, then you have done no research on global warming, as you clearly don't understand the problem. That he thinks that innate differences in interest between the sexes relates to the problem of including women in tech that is trying to be addressed by various "diversity" measures, shows that he doesn't understand what the problem is.
As long as you don't explain why you think it is not relevant, there'll not be much progress.
You could argue for example the default should be to treat the two(representation of women in tech vs psychological gender differences) different and "burden of proof" should be on the side arguing they're same. I think that's not obvious to me(and probably a lot of others).
The simplest way I can think of putting it is as follows: Say there was a chemical plant dumping large amounts of radioactive waste into a stream, and the population nearby is experiencing an increased incidence rate of cancer. People call on the plant to stop polluting, and the owner cites some papers showing that cancer has other causes too. Those studies would be completely irrelevant, and a clear attempt by the plant to find an excuse to not stop polluting.
That the participation rate of women in software is experiencing a sharp decline in recent decades, mostly in the US, (while, say, women participation in physics is on the rise) is an undisputed fact; that women working in software companies report abuse is a similarly undisputed facts. That is the problem we're trying to solve. That there may be contributing immutable biological factors is completely irrelevant. The main difference between this and the chemical plant analogy is that while there is no doubt that there are causes of cancer other than exposure to radioactive waste, the studies the author of the manifesto cites are very much controversial on purely scientific grounds, plus he clearly does not understand their context (e.g. that women in liberal countries prefer to work less etc. is no indication whatsoever of any innate factors).
But the main problem is this: Damore is no expert on the subject. His belief that the studies he cites are relevant is based on a layman's intuition, which is wrong in this case, as in many others. Explaining exactly the problems is much harder than bringing up ridiculous hypothesis by people unfamiliar with the subject like Damore. If you want to know exactly what the issue is (and I doubt Damore does, because he clearly read no research on marginalization of women), you should read actual scholarship on the subject, and not rants by some random guy.
Except for the citations.
> why I could easily tell that the author of the manifesto is both ignorant and uninterested in the subject
Continuing to attack the credibility of a largely factual statement (the memo in question) is still not compelling. If there was evidence supporting opposing viewpoints, even hypothetically, you might want to lead with that in your interactions. Good luck with whatever you believe.