Absolutely. So I am a person who grew up very much ensconced in Good Christian Values in the US and as an adult had to painstakingly deconstruct my cultural Christianity in order to assimilate into Jewish culture. It was hard work, let me tell you. It's been almost a decade and I still occasionally find things I need to examine.
Bottom line: I know what I'm talking about because I've lived it on both sides.
The US is absolutely saturated with cultural Christianity in general and the calvinist values of the original settlers in particular. The vast majority of people in the US are either Christian or culturally Christian. Because of this, everyone who does not do the immense amount of work to deconstruct those views and values and actively replace them with something different is going to be coming at the world from this viewpoint.
One of those views has to do with equating purity with integrity. Purity of thought, purity of actions, and purity of associations. Anything impure must be shunned and cast aside. Once someone or something has been deemed impure, you must immediately cut all ties too or you will also become impure.
I'm sure you can see how this plays out when trying to build a coalition around a specific area of advocacy: coalition building is damn hard when everyone you might ally with is viewed as being fully 100% endorsed for all topics and purposes by you once you ally with them. This creates three major problems: 1) You have a much smaller pool of people to draw from, once you've vetted them to make sure that you fully agree with them on everything, 2) it means that your cause must be every cause and you must form full-fledged opinions on every major topic regardless of whether it relates to your focus area, so that ultimately every cause is seen as so thoroughly related that it's hard to focus on just one issue, and 3) you ultimately end up with a bloc of groupthink, because to remain in the coalition (and therefore within its protection) you must tow the party line on the other issues. If you don't, you risk being cast out due to the purity of association thing.
The purity of actions piece makes it exceptionally difficult for people to come back from mistakes, which inevitably everyone is going to make. There is a process of sorts, but the "accountability" I've seen from the left is far less focused on learning from your mistakes and correcting the harm you caused to the best of your ability, and far more about accepting whatever unreasonable demands, public shaming, and abuse people want to heap on you for an indefinite period of time. There is no clear ending to it and no guarantee of real forgiveness, but it starts the second you flinch and admit that you screwed up. This process is so demoralizing and painful that many people leave and never return. The ones who do are unlikely to ever admit a mistake ever again.
The purity of mind thing makes it really difficult to interrogate these issues at all. Christianity itself has become something of a persona non grata in leftist spaces because of how terrible the church as an institution and many individual Christians have been to various minorities. So many people have deep, irreparable spiritual wounds from Christianity that discussing cultural Christianity or unpacking the ideas they absorbed from it is itself a trigger for their religious trauma. So things like the above analysis? Not something that is likely to happen unprompted and often gets a massive emotional reaction when pointed out to people by outsiders. Nevertheless, these ideas are all carried over from people's Christian or culturally Christian backgrounds and then never unpacked and examined critically.
And even if you can get past the trauma reaction, there is a huge barrier of understanding that cultural Christianity actually exists, is a real factor in society, and is something people need to be aware of. Namely: Christianity itself tries to separate itself from culture to be able to infiltrate every possible other culture, and therefore the very idea of religion-as-culture is difficult to fathom for those inside of it. There is a resistance to questioning doctrine and what has been deemed to be the right beliefs, and there is a resistance to understanding how this is a meta version of the thing itself.
Another mental purity thing that comes up is that Christianity has correct belief ("faith") at the heart of its core beliefs. If you stop believing, you are no longer a member in good standing, and that is also really the only way TO leave. Therefore, to leave, a lot of people simply stop believing in the core required religious tenets without unpacking anything further. Pointing out to them that there is much more work to do and in fact that it has just started, causes major breakdowns because they did the One Thing They Weren't Supposed to Do. They quit believing in the actual spiritual elements, and have accepted all of the fury and threats of hell that came with it. So if you say: "My guy, you just substituted this particular leftist work for the Bible and The Revolution for Revelations, you might want to reconsider that and look at how it's effecting your advocacy," expect waterworks and gnashing of teeth rather than introspection and commitment to change.
And as someone who's done that work?