I have heard that this is not as much of a problem outside of the Anglosphere, so if you are from continental Europe you might experience this differently.
Paradoxically it seems to be doing both at the same time. Here's a quote from the site:
> "For example, as the graph shows, in the 15 years between 1995 and 2010, the American academy went from leaning left to being almost entirely on the left. Similar trends and problems are occurring in the UK and Canada, and to a lesser extent in Australia."
How should I interpret this as something other than "We've seen a progressive shift during this certain period and we don't like it"? This says nothing about how diverse the opinions are - especially when you clump together a very wide spectrum of thought into "the left". For example, what goes for moderate/conservative ideas in the US translates normally to very hard right in many western-european countries (although admittedly less so recently), making it traditionally quite a fringe part of the political scene. But at the same time the European diversity of opinion is, in my opinion at least, far better than the essential two-party (both being firmly right-wing as well) scene of US politics.
> Instead the dominance of the left (at least in the US/UK) seems to function largely through socially-enforced orthodoxy, where dissent is punished and stigmatized.
This idea seems to be popular at the moment, but I can't find any proper backing for this claim - that one is disproportionately worse than its counter-parts - other than repetition.
I don't know if the left is any more guilty of orthodoxy, but as the left currently dominates academia, we can see more examples of the left enforcing orthodoxy in academic settings. For example, FIRE tracks campus disinvitations from both the right and the left, but the vast majority come from the left: https://www.thefire.org/resources/disinvitation-database/
I don't know if this is because of my European point-of-view but that site seems to be exactly the opposite. It seems to identify changes in opinion on universities as an inherent problem and that the former ratio should be promoted. Furthermore it clumps together far-left & liberal in some absurd common pool "proving" the lack of diversity of opinion. I mean a lot of European "diversity of opinion" is in precisely that single pool.