Those millions of people in the country who feel disenfranchised and who, it is implied, do - or, supposedly, should - disapprove of Corbyn's leadership, have the answer in their hands. There is nothing to stop them joining the Labour Party and supporting the MPs who wish Corbyn to go.
Corbyn set out what he believed in when he was persuaded to stand as leader, and he obtained overwhelming support. If support for him has dwindled because (a) some who previously voted for him have changed their minds and (b) some have joined the party specifically to vote against him, and therefore he loses, then presumably that will settle the issue.
What the MPs are trying to do now is ensure that Labour Party members do not get the opportunity to vote for him even if they wish to. I can't see how anyone can justify such underhand methods.