The NAP is a substitute for laws for “libertarians” who can’t tolerate the thought of other people actually being free.

The NAP is not a substitute for laws. I would argue that it is a framework, or set of principles by which laws are created. Also I do not understand what you are implying in the second part of that statement.

The entire point is to have something that proactively justifies the forcible imposition of your will upon others.

This is blatantly false. Libertarianism is fundamentally opposed to the idea of "the forcible imposition of your will upon others".

So the instant that somebody does something of which you disapprove, you can decree, by whatever rationale might serve, that it’s a violation of the NAP, so you’re now entirely justified in shooting them.

Can you define "something of which you disapprove"?