Well I agree with you that it's sexist, but your earlier post about how he deserves this level of kowtowing because he was the King really didn't come across as making a point about sexism.
He was an official consort, who did not rule, was not in the Line of Accession, and was not a blood royal. IMO that makes him a relatively minor and unimportant royal, and certainly in no way comparable to the actual Ruler of the country.
The comparison with Camilla and Kate I think is a combination of sexism and people being not well educated about these things, and also PR. Kate's PR team in particular have launched a PR campaign to promote what a perfect future queen she'll be, and because most Brits have only ever known a Queen as ruler, when we see the word "queen" we automatically think monarch/ruler. I've seen a few Kate fans in the past crowing about how she'll be the next queen in a way that suggests they believe Kate will actually be ruling the country and will have the same position and status as the actual current queen, which is simply lack of knowledge.
Our perceptions of and associations with the word "queen" are a direct result of having a Queen Regnant for nearly 70 years. I do wonder how that will change given we have (barring tragedy) three future kings lined up, and especially how Charles' reign will affect public opinion, depending on how long it lasts, and whether Camilla is styled as Queen or not. I mean if Kate was crowned queen tomorrow, it would be perceived very differently from 60-year old Kate being crowned after 20 years of substantially less popular Queen Camilla.