"BTW, you can find the answers to most of your questions on most any YEC website."
I agree. Visit some apologetics websites, read their answers and then do some research. That's what I did, and it answered a lot of my questions. Such as...
"Why do many Christians not believe in evolution?"
Because it contradicts a very literal reading of their holy book that is not even shared by most other Christians.
"Why do they claim evolution isn't scientific?"
Because they don't understand what science is or how it works.
"Why do they say evolution has been disproved?"
Because that is the conclusion they start with, then they try to find evidence to confirm it. When any piece of data does appear to confirm their prior belief they accept it uncritically, when it doesn't they deliberately drop it from consideration.
"Why don't scientists think their evidence is a problem for evolution?"
Because when scientists have looked at it, it has been trivially easy to spot the mistakes, omissions and misconceptions that have been used in its manufacture.
"Why do creationists say there is no evidence for evolution?"
Because they ignore or discount evidence that points in any other direction that the one they want to go in. Scientists follow the evidence, creationists drag it along, kicking and screaming, after them. Also, the same creationists who will discount any inference from the data as 'unproven' or 'supposition' will happily deduce the age of the Earth from the depth of mud on the sea-floor or dust on the Moon.
"Do they really believe what they say?"
If they do, then it is only through a pathological level of denial. If they don't then they are engaging in an equally pathological amount of deceit. Either way, they're not the sort of people I'd trust with anything I value (like, for instance, my child's education).
