Your response is somewhat an example of what I was talking about. By not clearly distinguishing between the different concepts you end up with muddled arguments.
You've clarified here and said that in the private case there is a 'moral obligation'. Really? What exactly is the obligation? Falling back on the generic notion of 'free speech' doesn't actually clarify the argument.
For example, if I managed a public forum for discussion of roller coasters, am I 'obligated' to accept all user generated content? What if a controversial post was about labor practices at an amusement park. Perhaps that is tangently connected to 'roller coasters' but maybe I don't want my site politicized and so I moderate/delete that content. Is that some sort of ethical violation (I'm assuming for this thought exercise that my terms of service say that I'm going to moderate content, i.e. this isn't a surprise to the participants).
What if my forum is oriented around a concept, such as regulatory reform? Is there an obligation to accept and publish content that is inflammatory, off topic, superfluous, or perhaps just contrary to my goals? What guidance would help me decide when I am 'morally obligated' to publish the content?
To be clear, I think there is value in healthy debate, I just struggle with the unqualified appeals to 'free speech' to put 'moral' requirements on publishers and unfortunately I think the power of the concept of 'free speech' is often wielded in these cases to advocate for legal requirements, which I think goes way to far.
EDIT: fixed typos