Ignorance is not opposed to intelligence. Arrogance is a flaw that can reduce the benefits of being smart, but it doesn't make someone not-smart.
(Unless you're using 'smart' differently to the conventional meaning, which is an unhelpful thing to do.)
I would've missed out on their insight had I applied a heuristic as simple as "arrogant people aren't smart".
Your reaction is an irritating trait of our western societies. Almost all our hero figures, all our geniuses, are arrogant assholes. Almost everything on TV is about a guy winning against all odds, our business geniuses had all crazy business plan, ... Yet, we despise the same people if their plan does not succeed.
Take a guy like Zuckerberg. Drop out of school to build your startup with borderline illegal business tactic, that's genius. Do the same and fail and you are an obvious loser that deserved what he got and should be happy not to be in jail. This mixed signal the society is sending is annoying.