What you say are words not facts too. It's your opinion, wrong but still your opinion.

I’m simply stating that for something to be objective it has to be an absolute irrefutable fact.

Anything else is subjective.

A UI can never be objectively bad because it is based upon how someone sees it.

For me, Gimp has a subjectivity bad UI because I’ve never been able to get my head around it.

Other people find it’s perfect and that it’s really easy to use.

Both statements are subjective.

“Objective” and “subjective” are both words that have well defined accepted dictionary definitions.

I suggest you to read some research on UX so you can understand that a big part of UX is in fact, not subjective. Like poor contrast cause reading fatigue on all humans, but at varying level. And that researchers determined a contrast ratio at which a certain percentage of the population can read without problems. And yes that's a recommendation because they can't force you to do it, so they recommand you to do it.