I'd recommend reading a bit through it, I argue throughout that the term "hivemind" doesn't hold much scientific validity as such, and not even it's antecedent variant, "deindividuation", works well for explaining social behavior under anonymous conditions (I choose to rely on the concept of "depersonalization" in the text, as it refers to strictly socially regulated behavior, as opposed to deregulated behavior as the two previous terms are suggesting").

But the semantics aside, the evidence points towards a trend of higher conformity to local group norms under anonymous conditions, which might be why we see behavior which often gets caricatured as representing a "hive mind" mentality. My view on this is that people are inherently very socially motivated, we seek affirmation of others, by others and want to relate to meaningful social units of sorts. To achieve this, we often rely on snap judgments of other people which is done largely outside of awareness, in which we judge "is this individual in one of my ingroups, or does he/she belong to an outgroup?". Based on the answer to this question, A LOT of further processing is determined, i.e. stereotyping etc, which will end up changing how you behave towards that person entirely. Under anonymous conditions, it's much harder to extract information about other individuals, so essentially we end up looking even harder for individuating information, and stereotype even more. If we judge that someone is an ingroup individual when we're communicating anonymously, people often tend to self-stereotype as well, which means acting in a way which is perceived to be like what the most "standard group member" (a "group prototype") would do. Thus ending up acting in a more conforming way.

It's a bit hard to explain convincingly in short, but it's well verified empirically. I think you'd get a good answer by reading the entire text.

Reddit is a good example, and I used reddit as a core influence when I was trying to verify different models's ecological validity. But if I would talk about the reddit community in relation to Fox News in social psychological terms, I would not say there's a "hive mind". I'd rather say that in the reddit community, there's a clear computer subculture norm, which is based around attitudes like strong intellectualism, high levels of skepticism, strong anti-authoritarian values, high valuations of individuality and personal achievement and a strong preference for political liberalism (in its broad sense, meaning both american style and european style liberalism). Given these attitudes, Fox News is perceived to be representative of an outgroup norm, for a lot of reasons relating to the reddit ingroup norm.

Since there's no room for use of the term "hivemind", I can't really talk about any hivemind bias. But there's definitely ingroup vs outgroup biases at work. Most people often don't process information from a source they perceive to be outgroup at all.

Note that in this case I stereotype the reddit community quite heavily. As all communities, it's more rich and diverse than any description like this can answer for.