A second referendum is not a re-run. The only way to have a rerun is to literally go back in time three years and hold the vote with the same electorate, having been given the same information that they were then.
I appreciate that "I would say that wouldn't I" is an easy rebuttal to my post, but it's also a matter of fact. The electorate has materially changed, the situation has materially changed, and referring the decision back to the people is, by definition, a further exercise of democracy. People are entitled to frame it in political terms, because of course one heavy motivation for holding a second referendum is to provide a different result -- but that can only happen if the electorate has changed its mind since 2016. There is no logic to the suggestion that, if the people of today have changed their mind, then they have no right to say so in a referendum.