There are two schools of thought about why Labour is adopting a confusing and conflicting position over Brexit which is almost the same as the government’s line. The first is that Labour is simply confused and conflicted. The more interesting is that this is deliberate triangulation: sound slightly less enthusiastic about Brexit to keep its core anti-Brexit vote, but also not to antagonise its minority pro-Brexit vote. I do not know which view is correct, and it is possible that both are. To the extent that it is triangulation, is this the right thing for Labour to do? This question is related to a recent Guardian article where John Harris argues that although Brexit will be a disaster it has to happen.
If triangulation is how Labour justifies its own position on Brexit, the obvious question to ask is why they made so much fuss when their predecessors appeared to triangulate over austerity. Brexit, like austerity, will be extremely harmful for the economy. So what made triangulation (or appeasement, if you want to use a more pejorative word) over austerity a huge political mistake, but allows the same for Brexit acceptable?
If you take the position that political parties and politicians should always argue for what they or their members believe in, rather than adapting their positions to what is politically possible or smart, then there is indeed no difference. Those who said that Labour’s failure to campaign loudly against austerity in 2015 represented some kind of moral betrayal should, for consistency, be arguing the same over Brexit.
A more political answer would be that in the case of Brexit triangulation worked, while for austerity it did not. In 2015 the election was all about economic competence, and Labour triangulation on austerity had the effect of conceding competence given the prevailing ‘clearing up the mess’ narrative. Of course Labour did not win the 2017 election, but they achieved during the campaign a surge in popularity that is virtually unprecedented. Labour supporters who are also anti-Brexit will tell you that this was because Labour made the election about austerity (or more accurately the size of the state) rather than about Brexit. If instead Labour had campaigned against Brexit, the election would have been a rerun of the referendum (as May wanted it to be) and because of the geographical concentration of the pro-EU vote Labour would have lost badly.
Even if you buy this, however, there remains a question of whether the triangulation strategy will continue to work, and whether it could have the unfortunate side-effect of ensuring Brexit will happen when otherwise it might be stopped. To assess this question, we need to take a realistic view of how the Brexit process is likely to evolve.
We know pretty well what the final deal will look like. It will be along the lines of the deal put on the table by the EU, together with a transition period during which we stay in the customs union and Single Market (and continue to pay for that privilege). We know this because the Article 50 process gives the EU the whip hand: the No Deal outcome, which is what happens if time runs out, is so much worse for the leaving country and there is no time to negotiate a trade deal.  As a result, to use a term loved by Conservative politicians but which in this case happens to be true, there is no alternative deal to be done.
The only risk before the election would be that the government would walk away. The election had made that much less likely. As there has been virtually no preparation for that outcome, it would bring chaos. This chaos would ensure that Theresa May’s successor lost any subsequent election. While the Brexiteers in safe seats might be prepared to see that happen, the rest of the party would not. Faced with a split in the Conservative party, Labour could not side with the government, as it would flip its triangulation strategy and lose a lot of its core support. As a result, a No Deal Brexit would fail. 
What this means is that we will leave the EU in 2019, but remain in the Single Market and customs union until both sides negotiate something else. Can a final deal of this kind be stopped? Logically you might think that MPs would realise that, compared to EU membership, all this deal does is mean the UK gets no say in the rules governing the Single Market and in addition we have to pay a significant sum of money for that lack of control! It is pure lose, lose, with the only positive (from a Leavers point of view) being the possibility of avoiding Freedom of Movement at some future date.
Unfortunately logic is something not normally associated with Brexit. In reality I suspect most Conservative MPs will agree to this (for the moment) softest of soft Brexits with a sigh of relief, telling themselves that they have fulfilled the will of the people with as little damage as possible. The triangulation strategy, which is essentially designed to prevent Brexit becoming a pro/anti party political issue, suggests Labour will go along with this. The only way either of these things might not happen is if public opinion turns against Brexit over the next year.
Will opinion move by enough to at least make it possible to get a vote for a second referendum through parliament? Who knows, but there are some structural factors against it. The first is the right wing press, which after all are the people who got us into this mess. The second concerns the broadcast media. Its operating model is based on a two party system, and if neither of these parties are making the case that our current difficulties are a result of Brexit then that case will not receive the exposure it deserves.
Here we get to why many of those who oppose Brexit are angry at Labour’s position. They feel that without a major party constantly reminding the public of the problems that Brexit is creating their chance of turning public opinion is much reduced. I suspect Labour’s response, if it was honest about what it was doing, would be to say that they will not risk the next election by taking a public anti-Brexit position. It is the Conservatives who got us into this mess, and they have to make the first move to get us out. The retort that Labour are reducing the scope of what they can do in government by allowing Brexit to happen has less force if we are staying in the Single Market and customs union.
This is related to the argument made by John Harris, which is that a vote to reverse Brexit would do nothing to reverse what caused the Brexit vote in the first place. If Brexit was stopped, UKIP would be given a new lease of life, and “the myth of betrayal ... would sit at the heart of our politics”. To recast what he is saying in my own words, you cannot undo social conservatism and the effects of economic deprivation, plus a decade or more of propaganda from the press, with a single vote of parliament. It is related to the earlier argument because Labour might say that they cannot reverse these same forces by a year of campaigning against Brexit before we leave.
Unfortunately there seems to be no reason why this state of affairs should change during the transition period. The government, committed to controlling immigration, will be determined to get a deal that ends free movement. Labour, to avoid immigration becoming too much of an election issue, will continue to triangulate. The best  hope I can see to avoid further Brexit damage is for Labour to defeat the Conservatives at an election, and quickly realise that they are better off staying in the Single Market and encouraging free movement. Which of course gets us back to why they are triangulating in the first place.
 It was designed in part to discourage countries leaving the EU. As David Allen Green suggests, there was a better way to leave the EU.
 We have gradually seen the government inching their way towards the EU proposals. (Remarks by Boris Johnson, like those of Donald Trump, are a distraction that it is best to ignore.) They are taking their time because the UK side has almost no power in the negotiations, and it is better to gradually concede to minimise any negative reaction among Brexiteers or the public. (Part of the problem here is that because the government still maintains a public stance that is pure fantasy, and the opposition wants to stay deliberately vague, the media feel unable to be straight on these issues with the public. It also requires effort to dispel fantasy with reality.)
 ‘best’ as in better than any other likely outcome.