I don't know why people give him so much credence. He's an expert in making entertaining TV shows. He's not a historian or an expert in any of the areas he discusses.
He's an artist who uses archive footage to tell a story. The story is often so simple that it isn't strictly true, but it's still worth a watch. I think his films will be treasured by future historians to get an insight into the current events of our time.
Historians pull their information from sources of all kinds. For example, a piece of propaganda from WW2 (which is likely to be almost completely untrue) could be an invaluable insight into determining a collective mindset of the time. Similarly, a diary of someone on the street, who's been taken in by that propaganda is also useful.
Adam Curtis exists in the outskirts of a behemoth of a broadcaster, so his interpretation of these events will be useful - especially given that they are broadcast so widely.
How can any one individual get an insight into a population of millions -- without making at least some concessions to practicality, and the generalisation and other "technical" untruths that this implies.
