If you take it as a piece of entertainment, more of a historical clip show with some connected narrative they can be enjoyable to watch even without trusting the information entirely.
Curtis has a gift of picking out obscure and interesting clips many of which were filmed before many of his audience (including myself) were even born. His British slant (and the fact that they come from the BBC archives) may make their relevance to those watching from outside of the UK particularly low however, depending on the overall film's subject matter.
I was being hyperbolic. The whole narrative with Syria for example is vaguely plausible but I really struggled to find sources to back up this grand conspiracy he very directly alleges.
Curtis has a gift of picking out obscure and interesting clips many of which were filmed before many of his audience (including myself) were even born. His British slant (and the fact that they come from the BBC archives) may make their relevance to those watching from outside of the UK particularly low however, depending on the overall film's subject matter.