Exactly -- I'm not sure why people seem convinced that YouTube should be legally compelled to provide free video hosting for anyone. Surely HN people should be aware how much that costs.
If one feels that YouTube is abusing a monopoly position, then one should be in favor of breaking up YouTube. Period.
I think in general people believe that freedom of association in business is a much more limited right than the other freedoms enshrined in the first amendment- particularly regarding not associating with people that you find disagreeable.
You cannot deny business to someone because of their race or ethnicity, and generally people think this is a good thing.
Legal theories aside, I think people feel that it is unjust when a monopoly or near-monopoly business acts in a manner discriminatory to one group or another.
The government has more than just 'breaking up a company' in their toolbelt for handling companies with dominant marketshares. It's not a black and white situation.
People can complain about something, without believing it is illegal, and without already having a legislative or other solution for the problem ready.
If nothing else, it informs others about Youtube censorship - even the most radical libertarians are pro-informed consumers.
If one feels that YouTube is abusing a monopoly position, then one should be in favor of breaking up YouTube. Period.