The dragons were actually dinosaurs of myth?

So…I was watching this documentary last night about how the creationists were trying to disprove evolutionists. The creationist scientists and the religious people in this documentary claim that the world was created six thousand years ago.
They are claiming that the dinosaurs actually walked and lived with humans at that time, they say that is why we have such a universal “myth” about dragons. They claim that there are cave paintings and statues of flying dragons which the “indians” (according to the scientsts) called thunderbirds but were actually the pterosaurs that were using thunderstorms to elevate them to the highest parts of the mountains to their nests. Also in the cave paintings there were pictures of dragons that were similar in look to Sauropods. These people were actually convinced of this and were using this to disprove evolution and the fact that the world is not millions of years old.
Their biggest “go to” was the fact that how did these ancient civilizations all come up with this one universal myth about dragons that spanned all four corners of the Earth? These ancients must have seen them in order to be able to paint pictures of them and carve statues of them and therefore they say dinosaurs actually lived with humans, but the word dinosaur was not around back then and they became sensationalized with fire breathing and magical powers to make them the dragons we know in faery tales and stories. They even cited Beowulf and said that Grendal in the story was actually a dinosaur that existed and that he was actually a Tyrannosaur and that the monster in that story fit the description perfectly. This documentary goes on and on about all these claims.
My question is how do you refute someone that think this is actaully how it is? Are we really just guessing about when dinosaurs lived on this Earth? I’m no palentologist but can’t we just shut this theory down by comapring bones of one of their anicent humans that according to them lived with these creatures with a bone of a dinosaur? I just cannot believe that there are people in the world that would believe this theory and I want to be able to refute it if I ever come accross one.