The OP is making the point that, for him, the method of making money is entirely relevant to his sense of fulfillment when working for a company. He does not make the claim that a business cannot be doing lots of other cool things alongside making money - in fact, he points out that Google and Twitter and Facebook are indeed achieving fulfilling goals, but he objects to the income stream and therefore would not feel fulfilled by working for those companies. That's completely fair.
Substituting the claim of the OP about "serving ads" with "making money" distorts the entire message, and of course makes it sound ridiculous.
I don't believe substituting "serving ads" with "making money" distorts the message at all. I think it merely highlights how immature his stance is. He stated quite plainly that Twitter isn't about connecting people, that Facebook isn't about sharing links, because they are about "serving ads". The implication here is that a company which sells ads cannot do anything, which is ridiculous. He set up a strawman.
Take the following:
> Google+ isn’t about sharing cat pictures, it’s about serving ads. Twitter’s massive network of 140-character bits of information isn’t about connecting people across the globe or to view current trends in worldwide thinking, it’s about serving ads. Facebook isn’t about entertaining yourself with games or sharing interesting links, it’s about serving ads.
Replace every instance of "serving ads" with "making money", and the meaning is unchanged, but the naivete is more obvious. You can do that to the entire article.
Every business is about making money. Whether they make that money by selling ads, or selling a product, or selling a subscription, or whatever else is irrelevant. Making money doesn't mean that a business can't also be connecting people, or organizing the world's information, or curing cancer, or any other fulfilling goal.