A bit odd this lawyer is demanding documents which his clients as lot owners would already have? Surely it is the lot owners and their lawyer who are potentially sabotaging a sale as the minutes and correspondence would reveal the situation upon a strata search by an interested purchaser?
Also, the lot owners cannot sell what they do not own or have rights over, and this defect in title could undo any transaction.
The issue is not one which could be resolved for the lot owners by any amount of threats or bullying toward the strata committee.
The nature of the lawyer’s correspondence appears somewhat unprofessional, perhaps even defamatory, and you are able to lodge a complaint about this type of behaviour.