"Women talk so much, am I right?" is a sexist statement, and it's particularly egregious when interrupting a fellow (edit: female) board member at an event announcing the new, non-sexist culture of the company.
I guess it depends a lot on the context and how it was said/meant.
Now this particular joke is pretty tame, certainly. If he wanted to he could have add the qualifier " more talking, bringing more perspectives to the table" or something. But the way he said it could have been interpreted as a stereotype, and therefore is problematic
i appreciate it when people do that instead of just downvoting - which doesn't exactly stimulate communication :) (It would be cool if downvoting on HN would only be permitted if also commenting...)