Conflating mainstreams

A thought I had over the holidays:

"Mainstream" is not, at any given time, a single concistant-seeming ideology. Rather, there are many different mainstreams, for instance a "western" mainstream and an academic mainstream, and in each of these there are various ideas and approaches which are mainstream. Also, people do not subscribe to or identify with "Mainstream" per se as they might to ideologies: mainstream is just composed of lots of things which many people hold to.
But people often act as though there were a single "Mainstream" ideology, or sometimes a single "Western" mainstream ideology, and it were one certain people subscribed to and other people didn't. Such people generally only portrey it as containing those mainstream ideas the disagree with.

What made me think of this was a TED video in which a non-dualist academic complained that it was inconcistant of he mainstream to be both dualist and anti-academic, but I suspect a simmilar thing sometimes happens less obviously.

So you consider there are several intertwining mainstream ideologies? or no mainstream ideology at all?

I view mainstream as being the default ideology. That what is the one's default opinion about something before he really starts thinking about it. It is also the ideas and opinions and theories that can be explained and talked about and referred easily and with few words, because people don't doubt them (you don't have to prove them the relevance of what you're saying) and people know what you're talking about. That's part of what makes mainstream ideologies so easy to have and use and propagate.

I guess that the fact the default ideologies can be conflicting is easily explained by how people don't really think about them, so they don't see these conflicting things. They don't even really care about knowing them.

I have a question I yet have to find a satisfying answer to, by the way : what are mainstream ideologies useful for? Why do people stick to it so much as they do?
The latter question could be answered to by saying that it's because it is frightening to have ideas no one shares. When you have ideas shared by everyone, you can rely on the other for the responsability of the idea. But if the idea is found stupid, and you're the only one having it, you're on your own to defend it, you can't say you were convinced by someone else, and you might even doubt yourself because of no one agreeing with you.