Question to native English speakers, can you please help me to understand this little nuance:

"They know all the talk of “openness to different perspectives” does not apply to causes of “social justice,” immigration, “diversity,” and “equality.” On this [sic] issues, you can either keep quiet or sacrifice your reputation and career."

So, "[sic]" here means that although it looks like it should have been "these" instead of "this", the editor understands that "this" is correct and should be kept despite initial impressions of a mistake. So, why "this"? It's not the editor trying to amplify the author's spelling mistake, is it?

The author of the original piece (Gideon) is quoting a different author (Brian). The "[sic]" is not about amplifying a spelling mistake, but rather to make clear that the quote is 100% verbatim.

"inserted after a quoted word or passage indicates that the quoted matter has been transcribed or translated exactly as found in the source text [sic]"

https://en.wikipedia.org/wiki/Sic