As I've pointed out, it is impossible for any Labour leader to change party policy on any issue between party conference. Party policy can ONLY be changed at the party conference. And, since it isn't possible that a second referendum will be approved in this parliament, with the Tories still in power, it's pointless to demand that Corbyn fight for the approval of something he can't cause the approval of.
I agree that some of the Brexit supporters are reactionary. But what progressive outcomes could there possibly be of fighiting to keep the UK in a body whose rules make socialism and even social democracy impossible? A body which can never be reformed or changed in any significant way? A body in which all major decisions will always be made solely by the EU Executive, with the European Parliament having no real say over anything?
Since no once but the wealthy in the UK would benefit from the UK staying in that organization at this point, why not accept reality that Soft Brexit is the only decent way out, and that what matters more than anything else is removing the Tories from power so Soft Brexit can be achieved?