If it's a success/popular you accept and move on, but seems daft to just vote for something you don't think would do any good.
On the face of it, your point is valid, but this policy is a massive, fundamental,
part of the reason for Brexit. The Brexit that has happened, and cannot be changed,
so it's akin to voting against Liverpool winning the league, and wanting it rescinded.
Yes, the opposition must oppose, but when that opposition is utterly futile,
directed at something, that has happened, been and gone, it's not clever.
If he'd have voted for it, as he's currently slightly ahead, his standing
amongst Labour red wall voters would increase, now, hearing this, it's
'Nah, no ta, still the same old shit.'