I would argue that Google has an obligation to be transparent, they do not have an obligation to be neutral. As you state, they are a private entity and can do whatever they want.
If news providers and other knowledge providers are allowed to curate what data they present then I don't think it's reasonable to demand that Google be held to a higher standard. Further, literally nothing is stopping you from creating your own knowledge aggregator if you feel that Google is doing a bad job of displaying pertinent data.
If news providers and other knowledge providers are allowed to curate what data they present then I don't think it's reasonable to demand that Google be held to a higher standard. Further, literally nothing is stopping you from creating your own knowledge aggregator if you feel that Google is doing a bad job of displaying pertinent data.