Earlier quoted context omitted.
An ad hominem attack would be attacking him for unrelated traits, i.e. "we can't trust people with blue eyes!" I believe his history as a snake oil salesman is highly relevant to his current "security" work.
Actually it's still ad hominem. The fact that you completely ignored the original post and instead attacked Steve Gibson, is indicative of an ad hominem attack. If you'd even said, this new idea is ridiculous because QR codes are inherently insecure (which is false) you'd be fine. Sources: http://plover.net/~bonds/adhominem.html I think this example is pretty much what you did. A: "All rodents are mammals, but a weas…
Also, you've presented no actual rebuttal of whether Gibson's history is relevant to evaluating his present claims. Rather you've merely stated the name of a logical fallacy. Which is, itself...