Well, I don't know. Let's suppose a minority civil rights activist wishes to post her call to action online, so she asks a hosting service run by old white men to do so. Do they have to host her content?

You're apparently taking the classic tactic of those who don't actually support free speech--I don't know if you support free speech or not, but this is the tactic which is used--which is to point out that it's not terribly hard to find speech that you and your debater agree isn't good.

But that was never the argument for free speech. The arguments are (1) the critically important speech is so important that it is worth tolerating the bad speech for--and there is no reliable formulaic way to distinguish between the two; (2) freedom is a very important virtue and free speech is very important as part of that--to be free of thought control, even more important than the right to not be annoyed by someone else's verbalized thoughts; and (3) it is only by discussing and debating ideas freely without substantial fear of censorship that bad yet emotionally appealing ideas can be raised and debunked and defanged, while good yet emotionally fraught ideas can be floated and gain understanding and support.

So with that as background, the questions are pretty easy to answer or dismiss.

Friedrich wants some flyers posted. The print shop doesn't want to print it. So, we ask: is the print shop a critical part of how ideas are disseminated and debated in society? If yes, then they should have to print the poster. If no, then usual rules of business apply--you and your customers have to be mutually agreeable to each other.

Ehud wants some flyers posted too, in response to Friedrich's. The print shop local to him doesn't want to print it (though they'd have gladly printed Friedrich's). Do they have to print it? Same answer!

The Buffalo White Supremacist wants his screed duplicated at the reprographic shop. Are they a critical part of how ideas are disseminated and debated? If yes, they have to print it.

The Buffalo Black Lives Matter folks want their list of demands to the Buffalo city council duplicated at another reprographic shop. Same answer.

Now B.W.S. goes to the ISP. There's already a pretty strong argument that ISPs really are facilitating the absolutely central part of human communication, so unlike with the photocopy shops where it's debatable, the presumption is that the internet is content-neutral, just like air, just like telephones. So they probably have a moral obligation to put up his site (assuming that it isn't a call to imminent violence--I'm okay with the normal legal distinction there; I think it's pretty much on-target since it doesn't contravene any of the main arguments for free speech).

The BLM people go to another ISP, and guess what? They get their site too.

That's how free speech should work.

There are additional caveats to make sure the three justifications for it are met. But the bottom line is that as a matter of pragmatic morality, those ideas believed to be bad are not hidden but rather are argued against.