"the torrent of scorn for conservative closed-mindedness confirmed my view that we on the left can be pretty closed-minded ourselves"

That sentiment reminds me of some of the comments from the "intelligent design" movement accusing the scientific community of being narrow minded for refusing to consider theories not grounded in evidence and methodical naturalism.

"First, stereotyping and discrimination are wrong, whether against gays or Muslims, or against conservatives or evangelicals."

In the narrowest sense this is true, but in the context of universities it must be pointed out that the scientific necessity of continual doubt, questioning and testing by experiment is essentially diametrically opposed to the mindset associated with evangelicalism. (If we are using the word "evangelical" here to identify someone who accepts religious doctrine as literal truth even in the face of empirical evidence to the contrary, which is how I would describe those rejecting evolution on religious grounds, for example.) Someone who is personally evangelical but able to conduct good science should of course be allowed to do so, but it is not at all surprising to me that a scientific environment is not an attractive haven for minds inclined towards evangelicalism and a poor environment in which to maintain such attitudes - science offers no guarantees of comfort.

"When a survey finds that more than half of academics in some fields would discriminate against a job seeker who they learned was an evangelical, that feels to me like bigotry."

To me it feels more like wariness about hiring someone for scientific enquiry who embraces philosophies that have shown themselves problematic when it comes to embracing the scientific method.

"I suspect many liberals disdain evangelicals in part because they don't have any evangelical friends."

There are many people who identify as evangelical who are very good people. Nevertheless, I would be careful about regarding them as qualified to pursue university level sociological research requiring the application of the scientific method to topics where conclusions based on empirical evidence could force them towards conclusions they would find personally uncomfortable. That doesn't make them bad people - they are often very capable in any number of areas, many of them very important to the overall health of society - but it does call into question their qualifications for research positions. For similar reasons, many who embrace methodical naturalism probably would have a hard time functioning as a professional religious figure. I'm sure there are exceptions in both cases, but the ability to handle both mindsets in one mind is not a skill set I would expect to be at all common.

"We liberals should have the self-confidence to believe that our values can triumph in a fair contest in the marketplace of ideas."

The problem is that for many groups currently identified as "conservative" or "evangelical" they have no interest at all in "fair" competition in a marketplace of ideas. That competition, by its very nature, involves subjecting to test and challenge ideas that those groups consider axiomatic. Inviting someone to subject the axiomatic foundations of their religious faith to challenge in a marketplace of ideas is unlikely to benefit anyone, least of all the scientific community.