Here are some examples since you have such a hard time with this whole concept.
Someone who actually saw Flight 77 hit the Pentagon with their own eyes is going to be far more credible than some truther trying to pretend they are a video expert and can say conclusively that it wasn't a plane in the security video footage. The eyewitness doesn't need an expert backing them up, but the truther is making claims as fact when they are, in reality, opinion. Now, if said truther were to wrap up all his findings and how he came to the conclusions he did into an article that could be submitted to a group of people who are experts at still video footage, he would have a chance to have his findings validated through peer review. His opinions would still be opinions, but those opinions would have MORE credibility due to peer review. Peer review doesn't mean there is no possibility for mistake. It simply means experts in the field of question agree with the findings of the submitter.
Another good example is WTC 7. Truthers just LOVE to pretend they know all about structural engineering and make claims like "WTC 7 couldn't have fallen on its own due to fires". Are they qualified to make that kind of claim all on their own? No. They're not. They may TELL you they are. You may even believe them. That doesn't change the truth, does it. Now, if they made their case for WTC 7 requiring a controlled demolition to come down, and it was peer reviewed and the experts agreed that WTC 7 couldn't have come down due to fire, one would not only have a MUCH more credible position on this board, but they would actually be able to approach the NIST and demand some answers. Do truthers do this? No. Why? Because they know as well as you and I know that their claims are nothing but baseless rantings of some seriously deranged people. They turn up their collective noses at all the studies done so far. They ignore the fact that, aside from a very small minority, engineers the world over understand that WTC 7 could and in all likelihood DID collapse due to its unique construction and the circumstances surrounding the collapse on 9/11.
Do you get it now? Do you need more examples? Do you still not get how you lied when you claimed Cooky and I were making claims we never made nor would we make?