While it is possible to Lock a filter so that users can't change it, sometimes they get confused by the presence of that filter and want to try to change it, which results in a support call to us. There could also be times when the filter criteria itself is sensitive.
We should be able to right-click on a filter and choose "Hide from Viewers".
This would also have the benefit of cleaning up the user interface a bit, so viewers don't have to wade through criteria that they can't control anyway.