Oh, as far as I'm concerned you won't have to leave a disclaimer. Sometimes maybe your posts feel a little like you're forcing your claim to appear objective, but that's something else.
As I think I pointed out, Science is one domain in which there can't be opinions, so somehow I agree. Evolution can't be disputed, despite not being 100% proven, and objectifying to it is indeed ideology. Ideologies are after all extreme opinions, that refuse to accept some facts in order to better promote others they view as "truth". A pure, genuine opinion, is indeed having an educated view on things that do not wittingly dismiss or disregard an element that could contradict that view.
I agree there are objective qualities to a work of art, and most of those you pointed out I can work with. There is no disputing the evolution of Art, its tools, or even the skill of an artist : me drawing a stickman will never hold up to Leonardo's sketches.
My view is essentially that objective qualities are a moot point if not supported by the people, essentially rich sponsors which was a required thing during Renaissance. Without the general public acceptance, a work of art will never become really "a work of art", but will stay forever or until ultimate acceptance "trash". There's been an ongoing development of art since the times of our ancestors painting on the walls of their cave, but I feel that, at any given time, that development would have been different if, say, Poussin hadn't been named First Painter of Louis XIII, or if the Medici hadn't shown much interets in art back in Florence during Michelangelo's time.
Obviously, everything human has been at one point steered by the ideologies of each eras, but while we can't dispute the results of Science, I will always feel like we can dispute the results of Art.
Science is all about hard cold facts : it's very binary. Art is more abstract, and most of the rules that dictate what is art and what isn't are at best empirical or culturally-driven. It's why, I think, Art is so heteroclite, and from one country to the other, style, material, favorite topics, etc will be so different
Or maybe I have this view on things because I myself walk a lot on the fringes of Art, where it's extremely hard to judge what is and what isn't...
