I don't see how the lack of intact skeletons has anything to do with the issue. The evolution of humans maybe, but not the existence of dinosaurs. All you need is a bone (well maybe more than one), replaced with mineral over time, and a method to date it and there is some proof to throw in the "dinosaurs existed, and a long time ago" bucket.
Maybe there is a vast, centuries old conspiracy where every museum in the world is faking every fossil, and maybe they have been successfully able to keep the charade up for all this time. Maybe every scientist in the field is in on it too. It's about as likely as the Illuminati controlling all the world's governments and bringing about a New World Order, but still possible I suppose.
I personally have not dug up a fossil, dated it, studied it and the environment it came from. I don't work in a museum so as far as I know, the plaster replicas of bones have no original and it is all made up. I have to take it on faith that fossils exist and they form the way I have been told they form. That some people are not convinced of what other people have told them doesn't really bother me. What bothers me is the wild jumps in logic, and willingness to embrace something super convoluted and unlikely over a simple if not entirely true explanation. I mean do these people really think it is more likely that all fossils have been faked, and all the scientific tests used to date things are wrong, and that people are competent enough to fool pretty much everyone in the world about the existence of dinosaurs for so long? And back to the group itself, their alternative explanation for everything is the bible. Their website says "Teaching others to deny the dinosaur lie and accept the lord", so their criticism in necessarily tied to their faith.
I guess anything seems rational when you believe in magic.
Here is the thing, they are not a group based on debating religion, they are a group of people who happen to be Christian and do not agree that dinosaurs ever existed. Their response to that is Religion and God are a matter of faith, while dinosaurs are considered to be a scientific fact, so they must be backed by heaps of irrefutable physical evidence. However, they claim that there is not enough physical evidence to prove dinosaurs did exist for it to be considered anything beyond a theory.
As for the MIC or Museum Industrial Complex, it would not really be a vast, centuries old conspiracy. Dinosaurs were not formally discovered until 1842, less than 200 years ago. The Bone Wars soon followed and lasted until the 1890's. Since then many of the dinosaurs "discovered" or classified during that time period have since been declared as false, mostly because the men involved were basically just tossing hunks of bone together based off how they wanted the dinosaurs to look, including the Brontosaurus which was recently denounced as ever existing. If there did indeed exist a Museum Industrial Complex, it would most likely be less than 100 years old.
Regarding the plaster replicas in museums, I personally looked into that and they are right. If you contact a museum that has a dinosaur exhibit they will confirm that they do use replicas and that the bones are far too fragile to display in the open. Not every scientist would be involved in the conspiracy, I myself am a scientist and like most scientists, have zero involvement with the field of paleontology. It would be a very small number of scientists in on it, mainly those with degrees in Sedimentary Geology and Paleobiology.
So their defense would be
The physical appearance of many species was conceptualized prior to fitting the bones in place (how?)
There has never been a fully discovered dinosaur skeleton discovered, only fragments.
Dinosaurs were not formally discovered until less than 200 years ago
An overwhelming amount of dinosaurs discovered during the bone wars have been proven as fakes
Museums make large profit off advertising dinosaur displays, but if questioned, they will admit they do not display actual bones....that being said, has anyone actually seen a dinosaur bone beyond those who work in the field of paleontology or museums?
Again, I do believe that dinosaurs did exist, I myself am not religious, but they can make a decent argument without bringing their religion into the mix. I can also see why they feel the physical evidence that exist could be considered flimsy at best. This is not all their ideas or reasons why, they have many more, I just am going off what I have seen them use recently.