The right to free speech in the context of the Constitution only applies when it's the government trying to restrict it.
The moral reasoning behind restraining the government from denying speech and other rights is that the government is a monopoly (in this case of force). This reasoning extends to restrictions on the ability of other monopolies, such as local utilities, to deny service.
If every service provider with the capacity to serve the needs of Website X were to deny service, the DE FACTO effect is precisely the same as a single monopoly doing so. In which case, the moral reasoning behind restraint of government and other monopolies comes into play.
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The Dayton shooter was a leftist, not a white nationalist.
I can't confidently say one way or another, but it feels more acceptable to me.
Assuming each company did reach that decision independently (and that's a big assumption) and not as a result of bad PR brought on by an angry internet mob.
The monopoly on violence does not necessarily have much to do with this.
The effect is the same, but the legal interpretation of the situation isn't, as long as new players are free to join the game.
You can find lots of examples where two cases of real-world events are the same, but are interpreted differently by law, depending on the context that is purely juridical.
> the moral reasoning behind restraint of government and other monopolies comes into play.
Governments hold the monopoly on violence, thus they are fundamentally different from any other entity.