We all adjust our language according to the audience. I would happily use terms like this in documents for the Open University. But in my day job, I produce process documentation. I would never put terms like ad hoc or ex officio in those, because the readers wouldn't know what they meant. All the councils have done is suggest that certain terms be avoided (not, incidentally 'banning' them).
This doesn't, of course, mean that I or the councils are advocating the expunging of all Latin derivations from English, or those derived from other languages. Words like 'virtue' or 'cul-de-sac' are commonly understood, so there is no need to find alternatives. To move the argument onto such vocabulary is setting up a straw man, unrelated to what the councils are actually doing. Referring to "ethnic cleansing" seems a bit silly.
At worst, the councils have been overzealous in the terms they have excluded. Most people probably understand 'etc.' or 'N.B.' (which are terms I've used in process documentation). But even the most obvious terms aren't always as broadly understood as you might expect - I've lost count of the number of reasonably intelligent and educated OU students I've had who don't know the difference between 'e.g.' and 'i.e.', so I can see the argument for using 'for example' and 'that is' instead.
The bottom line is that councils have a responsibility to communicate clearly to all people likely to be using their documents. It may be regrettable that this means many Latin phrases are no longer appropriate for use. But it's unfair to blame councils for acknowledging reality.