Oh yeah, that PLA question. I do plan on answering it. But that's a big topic, and as a college student, I have about 30 minutes of free time a week.
Overall, my point is that post-leftism is a self-referential philosophy. It has no basis but itself and its opposition to leftism.
Dot: the only real argument I made in that last post was my faux-argument for the post-leftists, which I'll agree is weak.
Amor: When the Edict of Milan legalizing Christianity was issued, it has been estimated that roughly 10% of Romans were Christian, still very much the minority. Before that, Christians had been persecuted by the Roman empire, limiting the spread of the religion.
After the Edict of Milan, Constantine, though never officially converting, used his power to endorse the spread of Christianity while oppressing traditional pagan religions. Constantine and his government was very much behind the spread of Christianity. It may have started as a lower class religion, but there was nothing special about Christianity as a belief system that caused it to become so widely popular, that was the work of the government. Constantine wanted a way to reunite a crumbling empire, and he did that with Christianity. The one aspect of Christianity that did really help its rise was the ease in which it could be used to justify the authority of the government, though polytheistic gods were used to do the same thing. Christianity as a philosophy crumbled soon after that, when it became a mandatory religion that people were forced to observe but not to understand (in fact, understanding it without the interpretation of government-endorsed clerics was strongly discouraged).
Also, universal progressivism is not an inherently Christian ideal. Back in the days before the enlightenment many Christian thinkers were degenerists, believing that the human race had deteriorated since the Creation. The idea of Universal Progress as you talk about it is actually a product of the religious cynicism of the Enlightenment Period. It was only once people started to reject the Bible as absolute truth that they could believe that humanity had been improving rather than deteriorating from a holy point of perfection, and it was only then that the idea of progressivism as opposed to degenerationism really took hold. Interestingly enough, progressivism was an important basis in the later theories of cultural and biological evolution (stage model evolution in terms of progress from "inferior" to "superior" stages has since been shown to be false).
We've already talked about the idea of progress, and I've already said that I don't believe that any culture can be superior to another, that's a baseless idea. However, I do believe that humans can work to improve their conditions as individuals and as societies. I imagine most people do, otherwise there wouldn't be much point in doing anything.
Finally, Lawrence, out of those lists of things that post-leftists promote/oppose, critical self-theory on the promote list and coalitions with leftists and solutions to problems based on failed history on the oppose list are the only concepts that are in any way unique to post-leftism, none of those ideas are very productive, and they only have a foundation (and a weak one at that) when examined in contrast to leftist ideas.
It's a rather obvious statement but one worth saying anyway: without the left, there would be no post-left.
The rest of the concepts are either misrepresentations or they are agreed upon by many leftists as well ("leftist" is a ridiculously broad term, encompassing a much larger group of ideas and people than "post-leftist" does, because post-leftism is a specific ideology while leftism is a huge collection of every other ideology except for post-leftism). For example, "ideological conformity" is a loaded term; most leftists encourage free thinking and critical comparison and combination of many ideologies, including post-leftism, which is an ideology.