What I think you are getting at with your question is that even in the way it is colloquially applied ("evil regime" / repression / lack of rights), the term authoritarianism is applied unequally. Actions that would be described as evil or authoritarian in somewhere like China are brushed off or ignored when they apply to so-called Western liberal democracies like the UK. To that I would absolutely agree, and I think that observation further speaks to the uselessness of the term in constructive dialogue.