[jjs]

> In a perfect world having a list where 25% of the names are potential trouble-makers [...]

... would be pointless, as a perfect world would have no concept of "trouble".

[steve19]

"in a perfect world" is an English phrase. It means, in this context, "if this worked perfectly".

It is not a statement about the world in general.

[jjs]

You say idiom, I say chronic lack of imagination.