I think he's totally right. If it were me giving the speech I would have amended it with "if they can", although I think he meant it that way. There are plenty of companies consisting of 3 people putting in 12 hour work days. I think it is safe to say they don't have to contribute back right this second.

However, if you own a company making hundreds of thousands a year from WordPress I think it is fair to say that while it is in no way required, the morally right thing to do is give back. If you rely on WordPress for your business, the better it is, the better it is for you as well.

Being a nice guy is always a good tactic, not just in business :)