You see this kind of problem on debates about climate change. Once people learn about environment and ecology they tend to assume that humans have an unavoidable impact on the planet. Climate change "deniers" simply have a different intuition. All the science in the world is not going to change that. Which is why it is political, and not objective.
Really the entire point of politics is to debate things that lack definitive truth. Of course that is probably true of anything that is discussed on a forum to a lesser or greater extent. Otherwise the answer would already be on Wikipedia.
But then, I guess, that person has every right to conflate moral and legal rights ... so sue me? :)