"Rational discourse on a mass scale about everything is difficult to attain, so frequently it goes on on a small scale, which then tells the public sphere what to think. It is not a good state of affairs, but it is easy to do, unlike rational discourse in which all of society takes part about all ideas."
Sure, but I think we can at least agree that where the individuals involved in a particular discussion have the capacity to hold informed, rational debate, they should attempt to do so. Yet this doesn't play out; I feel like I see a lot of people, even here on webdiplomacy, who have proved themselves capable of informed, rational debate, and then on some subjects choose the intellectually lazy way out with shaming. I don't really see the purpose from the perspective of seeking truth. (Of course, when truth-seeking isn't the goal, there's plenty use for it in shutting out opposing views. This is why shaming is so prevalent, on both sides, in political discourse.)
"When does an issue cross the line between moral and political? Abortions are a political issue, but one based almost entirely on differing moral values. Racism is widely taken to be immoral, yet racist policy is political. Is moral shame acceptable?"
I still say no, it isn't. Racism is pretty clearly a bad thing and it should be a trivial matter to vanquish racist ideas on their merits. Shaming doesn't assist in this venture. What shaming *does* do is legitimize rather harsh treatment of people who are revealed to be racist. This is not only incredibly problematic on its own, as everyone is at least a little bit racist, and thus potentially susceptible to falling into the crosshairs of shaming - it also creates a chilling effect with respect to espousing views which are popularly considered racist. When racist views are so easily vanquished in rational discourse, what benefit is created from this chilling effect? I see none.
Abortion policy is much the same way. It's actually even more of a mess since rational discourse has, to this point, been inconclusive in determining a singular proper policy position on abortion. So there's a real risk that mass shaming of one side of the abortion debate or the other ends up shaming the proper position out of the popular discourse. Even if we could determine what the correct position is, though, the argument from above regarding racism would still hold: shaming wouldn't enhance the discussion and would run the risk of creating an unnecessary chilling effect which can only be harmful to the discourse.
"And lastly, while shaming may have no place for anyone in a rational, healthy, liberal society, I do not happen to be in one. I can think of very few rational, healthy and liberal societies."
Certainly, but then that brings it own worry. Clearly we don't live in a rational society, but I'm not convinced that's the source of phenomena like shaming; like I mentioned before, there are plenty of intelligent individuals even on a relatively informed forum like webdiplomacy's who resort to shaming in lieu of rational debate, and do it often. While these instances represent individual failures of rationality, I'm not convinced the symptom is an inability to be rational. This implies that the issue is that we are no longer a healthy liberal society, which worries me greatly. Either we are a liberal society struggling to live up to our ideals, or we are no longer a liberal society.