I think it was Matt Taibbi who pointed out something I should have realized on my own. Words like 'whataboutism' are exactly what Orwell described in 1984 as doublespeak. Not a close match, not a good analogy, but the actual phenomenon explored in the novel.
If person A is allowed to do a thing with no repercussions, it is reasonable for a person B who faces unusually serious repercussions for a similar thing to point out the differential treatment.
Especially when the differential treatment is so commonplace and has a very obvious illegitimate reason, such as having membership in the legally-favored political party instead of the legally-disfavored one.