are there any liberal muslim communities which tolerate members leaving the religion?
That's a good question to add to the list.
If you leave the Church of England for instance, they don't really threaten to 'hunt you down' and most mainstream churches don't (they may encourage people to return which could be seen as pressure to some but it's very mild).
Being allowed to leave without any retaliation or threats is needed to be moderate and moderates would not treat people who have left any differently.