There is no evidence that Corbyn’s base among the membership of the Labour Party as wavered one iota. Those members who criticize Corbyn are those who have always been critical.
Labour remain voters are solidly sticking with Labour. If you look at the map of London wards won in pre-coalition 2010 and compare it with the results last week it is striking how the Lib-Dem revival is confined to outer London. There has been a miniscule recovery of the Liberal Democrats in the heavily remain inner London Labour boroughs. The only encouraging signs were Lib-Dem gains in Haringey and the success of the Greens in gaining 5 seats in super-remain Lambeth. Perhaps in the long run the Greens could cut into Labour support in inner London but we don’t have the long run if we want to defeat Brexit.
We have a year to defeat Brexit. Any scenario that sees us staying in the EU must involve Labour. If the swing against Brexit grows especially if we see formerly Labour Leave areas switching it will be more clearly in the interests of the Labour Party, say, to swing behind a Peoples Vote on the final deal. Corbyn opposed Brexit during the referendum and most probably he is simply agnostic on the whole issue. He can be pushed into taking an anti-Brexit line again. That would be greatly helped if a large section of his supporters are calling for him to make that stand. That’s why pro-Corbyn pro-EU are an essential part of our defeating Brexit.
That doesn't mean that Remainers should not criticize Corbyn. We certainly should be directing fire on Corbyn’s advisors such as Seamus Milne who there is good reason to believe has a hard line anti-EU position. But hostility to pro-Corbyn remainers is simply suicidal. If we ask them to choose they will choose Corbyn over the EU.
Those attacking pro-Corbyn remainers seem to me to be falling into the same trap that Corbyn supporters have so often been accused of. That is they care more about being numbered amongst the “virtuous few” than actually changing reality.
So please explain to me a realistic scenario in which Brexit is defeated without the Labour Party?