Why won't Remainers get behind Corbyn's Brexit plan?

At the BBC early doors for the Today programme, to preview Corbyn’s speech advocating membership of a customs union. I suggest that ‘this is something Remainers can get behind’, but come off air to a torrent of denialism and abuse on Twitter. In a parallel universe, the people who feel existentially destroyed by being halfway out of the EU would have made this case passionately before the vote, instead of trying to rely on fear and platitudes now. In quick succession, the European Commission drops its bombshell, obliging Britain to impose customs controls across the Irish sea; then Theresa May delivers her speech applying for a kind of off-peak gym membership of the EU. It’s well delivered, diplomatically calibrated, and doomed to be rejected. Again, in a parallel universe, David Cameron would have stayed in office, gone for something close to a Norway-style deal, with a cross-party committee to oversee the negotiations. Instead, we’ve got May and a shambles. I arrive at Newsnight’s studio to find the government hasn’t even put up a minister to defend the new position, allowing the sole Tory voice on the country’s flagship current affairs programme to be John Redwood MP, who spins it as a ‘take-it-or-leave it’ ultimatum. It feels like some realism is emerging about Britain’s practical options: it’s either a version of Canada or a version of Norway. The parallel universe does not exist.