Firstly, what is a "real" Labour MP? Someone who agrees with Jeremy as leader? Meaning anyone who doesn't agree with him as leader isn't really a Labour MP?
Secondly, is it democratic that any MP who mounts a leadership challenge faces the prospect of de-selection thanks to the recently drafted in £3 members who have rallied to support an anti-establishment hero, individuals who may never have actually voted Labour before in their lives, and who had little interest in the party until Jeremy decided to stand as leader? How exactly is it democratic that an MP, elected as part of the democratic process by their constituents faces being booted out a job for daring to challenge Chairman Corbyn?
I don't see those who subscribe to'New Labour' as real Labourites. I don't think new £3 members would have much power in Constituency Parties as yet, and it is they who decide to deselect.
Now we come to what is probably an undemocratic bit, but it's common to all Parties. The Electorate can only vote for candidates chosen by the Party. When you vote you are voting for people who have been 'selected'. I suppose it depends whether people are voting for the Party or the candidate.
However, those who select can also deselect. If they act contrary to the rules though, they can also be disciplined.
When the Coventry South East Constituency Party refused to abandon it's MP after his expulsion from the Party the National Executive suspended the Constituency Party.