I worked in the State Department, oooh sooo long ago, and fancy myself extremely well read.
I think "Well read" would be a function of the quality of the material as much or more than how much material you expose yourself to.
The relevancy of the opinions you form from that exposure would be very dependent on the context and accuracy of the material you absorbed.
Interestingly, you might could decode the context with some work but are still at the mercy of trusting the author to be correct and accurate.
As can be demonstrated by infinite examples, not all written, audible or even imagery based communications are without flaw. The presentation can flex in the direction that the presenter desires and yet still be labeled by the consumer as a benchmark resource for a particular subject matter.
I would guess that having a basic grasp of the subject would be the foundation for a person to expand their understanding and opinions by digesting what they can while at the same time considering the sources. Add in some objective reasoning and common sense to see if it passes the sniff test as well.
I guess I am saying all of that to say that being Well Read or even Extremely Well Read does not in itself automatically make one correct or even an authority on a subject. It would certainly provide a trove of information at your disposal to be used in a focused and civil debate but it is not automatically a sole qualifier to understanding the facts of a matter.