A second referendum only extends the mess, why should that one be definitive? There would have to be a tie breaker, unless it was an absolute landslide and I don't see that. The Leave campaign was infiltrated by all sorts of horrendous people but this was obvious to anyone who cared to check things out. There should never, ever have been a bloody referendum and it was one of the grossest acts of political selfishness and cowardice this country has ever seen but we can't go back.
Don't forget the narrative has largely been about how awful this all is, if we were to have a second vote the Leave vote would ramp back up again and spout the same populist, with an added line about the overthrow of democracy, I think they'd do just fine once again. If they were to lose it'd would be a small margin and what then? 1-1?
Also, if Leave were to win once again we would be even more beholden to the right-wing that we are now, they'd have the cocksure swagger of two victories and the more moderate voices would be swept to the side.