Even if that's the case, they're a very visible component of Reddit's userbase, to the point that an outsider definitely might see them as representative.
If the default home page and /r/all can all be flooded with posts about her, it's not exactly a small group of extremists.
It only takes about a thousand (net) upvotes to get something to the front page.
So a very small (less than 1%) portion of the visitors can very much get things like "fire Ellen" posts onto the front page, especially when there's no opposing block of voters.
(In other words, there were no passionate defenders of Pao who were eagerly downvoting the posts that trashed her. There were only anti-Pao zealots, and a much larger userbase that simply didn't care much at all. Count me in the latter, FWIW.)
If the default home page and /r/all can all be flooded with posts about her, it's not exactly a small group of extremists.