But, he asked, shouldn't its hidden functionality be treated as a bug or behavior that should be patched out ""to restore the application's neutral and intended functionality for all users equally?""

The intended functionality is very clearly not "neutrality", and this is very obviously not a bug. Free software does not need to be neutral, and has no obligations to be so. If it were truly an egregious change, I'm sure it'd be possible to rally the community around a fork of the software with the problematic content removed. I don't think there will be a lot of community support around removing this change, though.