Playing devil's advocate here (because I, personally, wouldn't have done something like that), but I can see the insult. Here's someone with a very public proven track record (that they're fully aware of, if 90% of their engineers use his software), and they're asking questions like this. They're the wrong questions to ask in this case, surely? It's fair enough to ask them, but I can understand this person's frustration if that was genuinely the reason he hasn't hired (which we have to take his word for, since we didn't witness it ourselves).