The Act only refers to non-member owners being able to attend and rather than you having to prove that they aren’t allowed, you can exclude them and leave it to them to prove that they are allowed (see below).
Even owners aren’t allowed to speak at committee meetings unless permitted by a majority vote of the committee.
Furthermore, Schedule 2 of the Act only allows for members of the committee to be represented by a non-member, provided they are approved by the committee. It doesn’t allow for proxies of non-member owners.
General meetings are different. Non-owners can attend as proxies. The process of electing the committee is part of the AGM but the election of office-bearers is a separate committee meeting, usually held AFTER the conclusion of the AGM.
I think it’s reasonable to allow non-owners to represent owners at general meetings, but not to allow them at committee meetings, especially if they are disruptive.
Keep them out of the committee room and let them pursue you to NCAT if they feel they have a case.
13 Non-member owner may attend
An owner or, if the owner of a lot is a corporation, any company nominee of that corporation is entitled to attend a meeting but is not entitled to address the meeting unless authorised to do so by resolution of the strata committee.