In an attempt to prevent an edit war over on Skeptics.SE, I'll defer to here.
Which is preferred - or are both correct?:
Was South Africa better run during apartheid?
or
Was South Africa better run during Apartheid?
Does apartheid refer to a government system like democracy (common noun) or does Apartheid refer to a specific government (proper noun)?
I would not capitalize "apartheid". None of the dictionaries I have checked capitalize it as a headword (MW, AHD, Collins, Oxford).
Capitalization, like punctuation, is one of the less settled areas of English orthography. I somewhat doubt that there is any definite answer about whether it is "correct" or "incorrect" to capitalize this word, so I won't attempt to answer that part of the question.
The Google Ngram Viewer shows lowercase as more frequent than uppercase:
This holds also for "during apartheid/Apartheid":
The Oxford English Dictionary does not capitalize it as a headword, and only includes, as far as I can see, one quotation where it is capitalized in a non-sentence-initial position (it is also enclosed in quotation marks in this context):
1949 Manch. Guardian 13 July 4/6 Thus Dr. Malan's policy of ‘Apartheid’ for the non-Europeans, which is only the Dutch word for Field Marshal Smuts's policy of ‘segregation’, which in turn is only a pretty word for repression, is achieving a position of ‘Apartheid’, in the literal sense of isolation, for the nation as a whole.
Compared to this, the OED gives about 10 examples of lowercase apartheid from the late 1940s to the 1960s, which are mostly italicized.
There may be arguments for capitalizing the first letter (at least in some contexts), but the preferred usage seems to be to write "apartheid" with a lowercase letter.
In the context you have, I would capitalize it, because it refers to a specific period in history.
However, if you were to use the word not as the name of a period, but to refer to the phenomenon, as in the sentences below, it shouldn’t be capitalized.
1. He hated apartheid as a policy.
2. A certain class reaped the benefits of apartheid without ever acknowledging them.
And even
3. South Africa wasn’t better run when apartheid was practiced.
See item 3.31 of the capitalization rules from the US government publishing office. Question 2 from here addresses both cases as does item 20 here.
If you’re using apartheid to denote an event, a period of time or era, then it makes sense to (https://www.grammarly.com/blog/capitalization-periods-and-events/). However, the only actual instances I’ve seen the word capitalized is at the beginning of the sentence.
If you’re using apartheid in the same way you would use the phrase “racial segregation”, then no. Although apartheid describes a specific system, it’s still a description.
I would argue both are correct in this instance because you’re referring to an event / period of time AND a specific system.
Since it hasn't been stated clearly by others (though some have alluded to it), I will offer a fairly "bright" (though still opinion-based) dividing line. Similar to "communist/Communist", the choice depends on whether you are referring to a concept or a specific state, party or institution.
Of course, deciding what is a concept and what is an "institution" is yet another argument.
Personally, I would never capitalize apartheid. Deliberately, in order to emphasize the despise for this indisputably wrong idea. Contrary to what dictionaries advise, I would do exactly the same for nazism or stalinizm, unless somehow any of them is used in a clearly positive context (which I cannot really imagine). But this is my personal approach.
As for facts, I guess people confuse two things. Cambridge online dictionary says 'Nazism', but at the same time there's 'apartheid'. My conclusion would be that 'Nazism' was the official doctrine of the German state, while 'apartheid' was not in the case of the RSA (though it existed there in practice as part of the social system). In Germany, there was National Socialism (Nationalsozialismus), the National Socialist German Workers' Party (Nationalsozialistische Deutsche Arbeiterpartei or NSDAP), consequently there was Nazi Germany and Nazism. As far as I know, the term apartheid was never used in such a way. It's just a common term to describe the social system of racial segregation in the RSA (Afrikaans for "separateness", or "the state of being apart"). It's a concept, so no capitalization by rule.
