I note that offering concessionary travel off-peak on buses is now
the law (although it would seem that offering them for
tube/train/tram is an additional "perk" in certain areas) and
wondered if the operator or issuer of the card has the right to
revoke the card if the holder is responsible for bad behaviour
(like what is /supposed/ to happen with the free bus pass for under
16s) and wondered if the same could happen with the Freedom Pass.

Visions of "Hells Grannies"! :-)

Funnily enough, I was actually thinking about whether it was allowed
whilst being given grief at work the other night from a passholder.
Whilst it was slightly irrelevant in my case (I work at a railway
station and his pass wasn't valid on the trains from this station - and
nonetheless I am sure he could have been removed under the
byelaws/Conditions of Carriage) it certaintly raised a few points in my
mind about the situation on buses.