Captain Kernow

Arrogance.

It means that they don't realise that "fiercely" is an inappropriate adjective for intelligence. As you say, intellectual pretensions.

I can only guess that it might be a reference to some people being "sharp" - and quick to spot / point out things - especially perceived flaws in somebody else's reasoning.

I could imagine some journalists (especially the political type), politicians and lawyers viewing something like this as a useful attribute.

Of course, certain others might regard this as a threat.

Some TV advertisers might also regard this as a threat - especially if certain viewers might be able to quickly "unpick" some of their carefully crafted adverts, then come up with subversive adaptations.

I happen to know that some engineers are very skilled in this regard - and generally being quiet, easy going and mild mannered isn't a block to this. In all honesty, this might not come as too much of a surprise to some people - as, in a number of college engineering courses, people are taught to pick apart manufacturers' data sheets etc and design projects based on worst case assumptions.

In other words, some people might regard "worst case design" as a form of calculated cynicism. "You might very well think that. I couldn't possibly comment."