I have never joined any political party although I am not saying that I never would in order to achieve an aim.
However, if a person has been a member of a political party for many years and that party moves with the times in order to get elected and bring about some reforms why should that person leave the party when it gets taken over by old-fashioned instead of forward-looking politicians controlled by a somewhat shadowy movement and, thus, as many would say, making themselves unelectable?
Would it not be better to work within that party with like-minded politicians, party members etc to try to bring about rational policies together with a leader who could make that party electable again.
Carrying on down the same, so far unelectable, route is not going to achieve the aim of replacing the Tory Government. Introducing de-selection will mean many good and popular MPs could be lost and Labour could spend even longer in the wilderness.
Jacob Rees-Mogg Moves For Conservative Party Leadership.
Leadership without a GE means becoming PM - and sniggering posts about Jacob Rees-Mogg will achieve nothing because he will not become PM.