Years in the
business of technology definitely mean something in relation to both IP and lawsuits. The former being a key ingredient to tech businesses, and the latter being a a risk you must consider any time you sign a contract.
The fellow clearly says that, having been through a couple of lawsuits, that it's tempting to react to the initial wave of emotion. So he's not questioning Carmack's knowledge, he's using Carmack's situation as a handy illustration of his point.
Also, his advice isn't to shut up until trial. It is to wait out the initial wave of emotion, to talk to your lawyer, and think things through until you are truly ready to speak on the permanent record. Which is indeed bog-standard advice.