Post-industrial America and the Proletariat

Frankly I don't have any sympathy for someone who takes an authoritative position for a higher wage regardless of how much extra work they have to put in, your primary role as a manager (even a low-level one) is to take power away from the low-level workers. If the workers are working too slow, you whip them to go faster, if they are not productive enough, you whip them until they are, if they are discussing unionization, you report them to upper management, it is an inherently oppressive occupation, they are literally representatives of the bourgeoisie on the factory floor. At the very least they are lumpen, and the worst they are outright class traitors.

Capitalist commodity production involves productive capitalists purchasing both productive and unproductive labor labor. The productive labor power is what produces the surplus. Unproductive labor could be anything from supervisors to fixing the machines. The capitalist isn't combining the laborer's labor power with equipment and raw materials to produce commodities

If they're an independent contractor that might be true, but if they work for a company that contracts, they're being exploited.

Just because you're not the one pulling the lever to make the widget doesn't mean you're not part of the production process. You are effectively arguing that janitors are not exploited because the capitalist isn't selling a clean working environment.

Marx wrote about this, you know.
marxists.org/archive/marx/works/1863/theories-surplus-value/ch04.htm

A janitor isn't a part of the fundamental class-process and produces no surplus for a capitalist, he's not a productive laborer. Don't attach a value judgement to the word "unproductive", that doesn't mean they're useless.

I think there is a misunderstanding here, unproductive-labourer is no a pejorative term, they are literally necessary for the function of any society.

This defines productive labor as labor which is exploited, not labor which produces physical stuff you illiterate.

Yes, and janitors and supervisors at work do not create capital. They're not exploited in the Marxist sense of the term where a person who performs surplus labor has it appropriated by another. Capitalism involves PRODUCTIVE laborers being exploited by PRODUCTIVE capitalists.

Supervisors may not be but janitors are paid less than the value their work adds to the means of production by keeping the workplace maintained. You're getting hung up on layman definitions of these words instead of reading what Marx actually says here. Anybody who's paid less than the value of their labor is contributing to capital because porky uses that surplus to reinvest in capital. It's the same whether you add value by assembling parts, moving parts, cleaning waste, etc.

If the difference is entirely academic then what's the point talking about it?

This.

Marx doesn't talk about janitors, retard. He's talking about commodity production.
No value is added here.