While I disagree with their conclusion, they do have a point, debunking a miracle claim does not prove that miracles don't happen. No matter how many miracle claims are shown to be false, we can't say for certain that other miracles don't occur. This goes for pretty much any debunking that we do, whether it be horoscopes, water dowsing, or psychics. No matter how many times you show a claim to be fraudulent or simply mistaken, there is always the possibility that the real deal is out there somewhere.
Of course, I didn't immediately stop believing in UFOs, this was just a stunt by the discovery channel. The fact that humans can also make crop circles doesn't prove that UFOs can't make them. I remember watching other shows which also debunked other UFO stories, and for a long time I just figured that UFOs are cool, and people will want to create their own, and hoaxes are probably fun to create and trick your friends with them. Even if 99% of UFO claims are shown to be fraudulent, it doesn't prove that the last 1% are also fake.
But then I started to ask myself what I thought was more likely, that the rest of them were also hoaxes or that aliens really are hanging out around our planet and hiding. It seems much more believable that some people creating hoaxes are just really good and set things up in such a way that it is nearly impossible to debunk. Also, once I learned about how big space is, it really doesn't make sense that an alien race would screw with us for decades but never reveal themselves. If they were to travel all that way, you would think they would make contact. Ultimately I decided that believing in UFOs was silly.
I think these miracle claims are very similar, no matter how many miraculous statues are shown to be the simple result of a broken water pipe, it's always possible that there is another one that is the real deal. But at what point does it seem more likely that the next miracle claim will also be fraudulent?