If you reduce everything that Lyons is saying that that one quote from the CEO, perhaps the evidence is slim. But if you take the observations he's making together, as a whole, a different picture emerges:

The place was like a frat house, with refrigerators stocked with cases of beer and telemarketing sales “bros” drinking at their desks while hammering away on the phones. Thirty-something employees were considered “old people.”

And of course the quote about HubSpot “trying to build a culture specifically to attract and retain Gen Y’ers,” also attributed to the CEO.