Dissent, and anti monarchy sentiment, is as old and as 'British' as the monarchy itself.
If you don't understand that , you don't understand much, nor do you know your history.
It makes for a simplistic, inaccurate world view.
Like you say it's black and white thinking, which actually serves no one very well.
Unless you particularly like ignorant narrow mindedness.
I was around for the 77 jubilee, there was no 'unquestioning' acceptance nor idealising of the institution of monarchy then, any more than now.
Fwiw myself, and all my forebears are English as far back as anyone knows .
Unquestioning acceptance of hereditary privilege, and power is not a requirement of Britishness, nor Englishness for that matter
Unquestioning acceptance of what your country does, right or wrong is not patriotism, it's nationalism, which can easily slide into populism and even facism .
Not being able or allowed to intelligently critique your government, or your countries institutions leads to authoritarianism..
You know, like in China, Russia, and other bastions of freedom, and free speech..
Sorry forgot you won't read this..