Because news papers and magazines review all their content by hand (and usually make that content themselves). The comparison you're making is like seeing a weekly neighborhood get together where everyone joins in except the black family which is excluded and saying "Well what about all the other private homes that black people never enter?". Those other homes aren't having a neighborhood get together, it's a different thing.

I don't think it is! Major social networks behave more similarly to magazines, newspapers, publishing networks than they do communication protocols that put you directly in touch with someone else (email, phone, letters).

I think a lot of people hold this philosophical belief that social networks have some sort of responsibility to be fair on everyone all of the time, but I don't really see how companies are incentivised towards that in any way.

There is a sort of ethical question, that in the same way that in theory news organisations should be honest, diligent and accurate that social networks do have some sort of responsibility to be fair on everyone.

It's just not enforceable currently, and I feel like trying to force that sort of integrity onto social networks isn't currently viable.