"Fools should have read his memo a couple of times before responding, but then how many right-on liberals do that?"
It's actually up for debate whether this is necessary. And I know that sounds horribly dismissive, but ... well, I suppose as a not-right-on-liberal type, you are obliged to read all of this before dismissing it, haha.
Anyway: in the specific case, this guy writes that " Many of [the biological differences between men and women] are small and there’s significant overlap between men and women...", and his argument essentially then goes on to claim that these factors are largely behind the gender gap in employment. But what is a "small" difference going to lead to, in a world with no other contributing factors to the gender gap? I think it's safe to say that, rather than about 50% of tech engineers being men, maybe it should be 55% or something, in an ideal world, to account for the "small" differences that he implies. But Google's computing engineers are 80% men. That is clearly *not* a "small" difference, right? So it is surely reasonable to conclude that there is some other, more significant factor at play.
Then, the reason you might not feel a need to read the rest of what he writes is that you can reasonably, from the above, conclude that the entire premise is flawed. "Small" biological differences are incredibly unlikely to be the entire driving force behind "large" disparities in gender make-up of a workforce, and as his argument seems to overlook this then that's the first question I would ask him to address before moving on to critically discussing anything else he says.
There are also a couple of factual inaccuracies: for example, the writer notes that the differences between men and women in society are "universal across human cultures", but this is not correct, and several societies exist or have existed that have a matriarchal structure. They are rare, but it kills the "universal" claim stone dead.
But in general it sometimes follows that you can very quickly evaluate the strength, or otherwise, of an argument without having to read it all the way through. This isn't a leftie liberal thing, it's just common sense. If someone starts off a scientific paper, for example, claiming that the Higgs boson is actually just an atom of Xenon and attempts to justify this by noting that "four muons weigh almost nothing so how can a Higgs boson turn into four muons and where did all the mass go?", then at that point you just stop reading because the rest is also guaranteed to be incoherent rubbish. (I have not made up this example; time was when I, and the rest of the physics community, would receive this email once a week for the better part of five years).
It's a judgement call, and I will certainly grant you that there are times when I've come to that judgement too quickly, but on the whole I think it's reasonable to assume that if a long post starts right off the bat with something that is factually wrong or leaves a glaring hole, then you want them to fix that mistake or fill that hole before wasting any further time on the rest of what they say.