I was addressing the points you raised.

There are no "natural rights". There are the rights granted us by the Constitution. That's it. If the Constitution changes, our rights change with it. Usually for the better (i.e. given new rights, like women's suffrage, or the right not to be owned as property). Then there are laws which can refine rights (e.g. in some places you have to try to escape before you can exercise "self defense", other places allow "stand your ground").

The justification is necessary, but that justification is the Constitution. Which is interpreted by SCOTUS. They render really bad decisions (like Dredd Scott, Heller, and "money is equivalent to speech"), and some really good ones (e.g. the "you can't discriminate against people" decisions). Which is where the arguments arise, and message boards and media light-up from time to time.