It's not about being insulted, it's about understanding the mindset of Congress. The fact that even the anti-SOPA people see engineers that way is even more concerning.
I think this all makes a lot more sense under context. As I recall (I watched the first two hearings, nearly entirely), somebody asked a technical question like "What are the consequences of [something]?" and one of the supporters of SOPA said something like "I don't know, I'm not a nerd" and that prompted the opponents to respond with "Exactly! We don't know! Let's go ask a nerd!"
tl;dr: They started it :-p