What is for the public benefit?

What is for the public benefit? 
On what basis do we decide that? 
Are those criteria obvious? To who?
How do they know their criteria are right?
How do they measure benefit? 
How do they know that they've measure right? 
And why should I or anyone else accept what they say?

I've have these questions in my mind for awhile. So I found myself reading the Charity Commission's booklet:  Charities and Public Benefit.

I can't believe it. But I did. 

And murky is the way I would describe it. I'd be delighted if someone would show me a clear paragraph explaining exactly what this concept of 'public benefit' is, how it is measured and judged. 

The best I got was this: 

There are two key principles both of which must be met in order to show that an organisation's aims are for the public benefit. Within each principle there are some important factors that must be considered in all cases. These are: 

Principle 1: There must be an identifiable benefit or benefits
Principle 1a It must be clear what the benefits are (see section E2)
Principle 1b The benefits must be related to the aims (see section E3)
Principle 1c Benefits must be balanced against any detriment or harm (see section E4) 

Principle 2: Benefit must be to the public, or a section of the public
Principle 2a The beneficiaries must be appropriate to the aims (see section F2)
Principle 2b Where benefit is to a section of the public, the opportunity to benefit must not be unreasonably restricted: (see section F3)

But this section begs all the questions that I have! It must be a field day for the lawyers. 

(Oh, right, I get it now!)

But the reason this matters is not first of all because lawyers will get fat on it. Though that will bring problems and victims - many of them unseen and unknown to us (not to God). The reason it matters is when someone (or the majority of people ... 51%?) thinks the way Bertram Russell does, and they come to define and enforce public benefit all religious charities will lose that status: 

The question of the truth of a religion is one thing, but the question of its usefulness is another. I am as firmly convinced that religions do harm as I am that they are untrue. Why I am not a Christian: and Other Essays on Religion and Related Subjects (Routledge Classics)