This - and yesterday too - seem especially angry. Maybe it's in response to what happened the day before. Maybe it is leading up to a breakdown. I wouldn't worry too much though. Dilbert recovered from being shot dead by "dear hunters".
He's being insulting because he knows no one is actually paying attention to him. He's experimenting. He wants to see how outrageous he can be before someone will take notice, and as he correctly hypothesized, even after the insulting comments the listeners are too dumb and uninterested to notice, hence the 'Are you taking questions?' response.
The people in the audience are only asking about questions because, like most presentations, they only care about the part that's relevant to them or their department.