The verb "discriminate" has been (perhaps rightfully) saddled with negative connotations, but discrimination is exactly what any hiring manager is doing. You're discriminating between candidates on the basis of non-protected attributes. Obviously we don't want to discriminate on the basis of protected attributes, and it gets messy when there are areas of strong (often causal) overlap between protected classes of people and the non-protected characteristics that employers are looking for in candidates. But that doesn't obviate the need for discrimination along
some axis or other. (Hard technical skills being the example that is probably most salient for the HN crowd.)
In an ideal world, anyone could do anything they wanted without impediment. But to quote Mr Lightyear, we're not on that planet. In this world, if I'm hiring you for a role where you're responsible for safeguarding the wellbeing of others (teacher, manager, doctor, whatever), then of course it's going to put downward pressure on my ability to hire you if you have a super fucked up background that makes you snap at people, attack them without provocation, jump at shadows, have traumatic flashbacks mid-sentence, whatever. I'm sorry, but that's just how it is. There are other jobs that are better suited for people in those situations.
Regarding "culture fit":
While we should try very hard to avoid promoting monocultures when hiring (for a whole lot of different reasons, particularly because diversity is crucial for organizational resilience and adaptability), the truth is that it remains a very subjective determination. It depends on your criteria for what constitutes a monoculture. You could say that we live in a monoculture with regard to our expectations for treating everyone in the workplace with a baseline amount of respect. But not everyone agrees where that baseline should be drawn. If you come into an interview and it's immediately clear to me that you're the kind of employee who's going to be disrespectful of your coworkers, and I reject your application accordingly -- well, I'm promoting a sort of company monoculture in that sense.
Then you can walk back from that into varying shades of grey regarding different individual's varying ways of signaling respect, or deemphasis of candor in certain situations, unwillingness to openly address issues, etc, and it gets very messy very quickly. Where is the line between avoiding hiring rude people and discriminating against people from backgrounds or cultures that have patterns of communication that others may perceive as rude? And so on. It requires great care.
This is the sort of ambiguity I'm talking about. To think that this ambiguity doesn't exist, or believe that we can simply wish it out of existence -- that's why I reached for the word "naive" in my original post. I think a lot of engineers are fortunate to work in positions where they don't need to wrestle with this sort of ambiguity in their day-to-day.