If the low paying, menial jobs are indeed essential, why are they low paying? Do the people working these jobs currently really have a choice? Is that morally justifiable?
These jobs are low paying because competition is high between low-skilled candidates: "if you don't want to mob the floor, you're fired, I'll find someone else".
Do these people have a choice ? They usually have a choice between many low paying jobs.
Is it morally justifiable? If you believe meritocracy is a bad thing, then no. If you think it's a good thing, then low paying low-skilled jobs are just a fact.
Guns, thugs, police, arrests. That kind[1].
>If people want to unionize they are free to do so.
Well they're not[2].
[1] -- http://en.wikipedia.org/wiki/Goon_squad [2] -- http://en.wikipedia.org/wiki/Union-busting
Oh, and then there's the issue that property in the means of production is itself a relation created by the capitalist state, as are the modes of its organization (ie: joint-stock companies instead of commons trusts or workers' cooperatives).