I think there tends to be a general distrust of the FDA as their main goal seems to promote and keep certain industries (agriculture, being one) strong without much overall regard for "human safety."
For example, they go after people who sell and manufacture milk the old-fashioned way. What harm could possibly come from that? Oh, right, reduced homogenized milk sales! Can't have that, now can we?
In essence, I agree that the FDA should look out for human safety and I agree that supplement and drug companies have been able to blow smoke up our collective asses for far too long.
But when I look at substances which aren't controlled like alcohol and tobacco, substances which are tightly controlled like "gear," and look at how some drug companies are able to garner approval for drugs with a laundry list of side-effects including paralysis or worse, the reality of how the FDA works falls far short of my ideal.
Complication makes it easy to explain failure.