Paul Graham is primarily making an observation -- he's a venture capitalist, and he doesn't find that people who didn't start hacking early are the kind of technologists that make him a lot of money. That doesn't specifically make his comments good or bad, excusable or inexcusable. But that's where he's coming from.
There's a huge outcry, of course, from people talking about how you don't need to start hacking at 13 to be an amazing programmer (and you don't.) The implication behind these things is that a woman with fewer years of experience should be every bit as good as a man with more years of experience.
Speaking as an old guy, I have no idea where to go with this. Because the argument that goes "more years of experience don't make you better!" makes me look like a pretty bad choice of employee. I'm a lot finickier about working conditions than when I was younger with fewer years of experience, for instance.
To be fair, startups already tend to discriminate against old guys (Paul Graham and Y Combinator less than many). And getting more young women in startups would be good all 'round.
But it looks an awful lot like this argument is a straight-up tradeoff of their advantage for older workers'.
I have quite a lot of advantage, and I can give some up. But "we should discriminate less against women in tech and more against old people" is still kinda mixed, you know?