How is this "universal truth self-evident"? I'd love you to show me that there is a repeatable and measurable experiment that determines that as a fundamental

How is this "universal truth self-evident"? I'd love you to show me that there is a repeatable and measurable experiment that determines that as a fundamental function of the universe, people should have equal rights. Personally, I don't believe that (the fact it's a universal truth) to be true, morals and ethics are a subjective topic and stuff like "everyone should have equal right" is something that most people including me can agree on fairly easily. Other people might not agree.