"The fact a set happens to be showing a given programme does not tell you how many (if any) people are watching it."
Sadly not relevant. The exact wording of the TV licence is that it is a licence to receive TV broadcasts
To be fair, that comment was referring to a previous comment about how requiring a licence number to even recieve the iPlayer stream, would help with accurate viewing figures rather than them just plucking an estimate out of thin air. It wasn't actually attempting to argue that an unwatched TV was exempt from the licence fee requirement at all, which is what you appear to think it was saying.
Personally, I think the argument the BBC is neutral, and must remain neutral, and that is why they must be funded in this fashion, is old, tired and irrelevant. It gives them licence to produce a never ending stream of vomit with no reason to improve because they know they don't need to... they get paid, whatever happens.
They should bloody well be forced to produce quality programming, and if that means them having to source income on an equal footing as other broadcasters, then so be it. Sure, I understand that ITV, C4, and Five all get a percentage of the fee nowadays. But the fact that they didn't originally, and all of them thrived using advertising instead of TV licensing, should be enough to prove that it's a viable option.
Of course, at least under this current system, those without a TV have a good enough excuse no to pay. Which is better than the way the BBC wants and was floated in parliament by the Culture Secretary of the day. They wanted to scrap the TV licence entirely, in favour of a broadcast tax, which would be administered to every household regardless of if you even had a TV, similar to the broadband investment tax that BT wanted to introduce.
Yeah, because that just seems so much better...