You raise a good point. but if this is the only information source you have for supplements and all things concerning the gym then you are a moron.
Anyone with any intelligence would find multiple, often contradicting sources and form their own opinion based on reason and logic.
For example, if you were only to read books on the pro of Marxism I am pretty sure you would end up spouting how great communism etc is.
It is not balanced, to get any rational perspective you would have to read many books concerning all political and governing styles.
Don't put all your eggs in one basket. That way you wont have to ask people if the basket is reliable, instead you will be able to conclude from using many other baskets and having used baskets in the past if aforementioned basket is up to scratch.