Just like in the U.S., the UK's left won't accept the results of a 2016 election.
Labour has been a big curse on Britain ever since the Attlee years. They need to be kept far away from power; imagine Corbyn as PM and his other openly-Marxist buddy John McDonnell (who recently referred to Churchill falsely as a “villain”, citing old lies about the 1910 Tonypandy mine riots in Wales) as deputy PM, with the possibility of passing bills of attainder still legal there?
It makes sense for moderates to leave a far-left anti-Semitic party — British Labour or the American Democrats, for example — once they’ve lost all hope that moderation and decency can be restored there.
Seven Labour moderates have reached that conclusion and left.
When will similar lightbulbs go off for American Democrats? When moderate presidential candidates like Joe Biden are mocked, attacked and ridiculed 24/7 by far-left anti-Semitic Democrats to the point that they can’t get beyond 30 percent in the polls?
Brexit has been the main but not the only catalyst for this. The result of defections is likely to leave a void in the centre ground which may, or may not see a new party emerge. (Remembering the SDP and the 'Gang of Four', I'm not placing any bets.)
The “seven” are afraid of Brexit, not going far-left, not anti-semitism.
This is a bid to delay, fudge, re-vote, STOP Brexit at any cost.