Are you saying these people just don't understand and haven't taken the time to learn the details about evolution? Or, do these people understand the science behind evolution and still actively deny that it took place? If the latter, then yes these people aren't "all there". Perhaps calling them stupid is over the line, and counter-productive, but I would be skeptical of any other opinions they hold due to the fact that they are creationists. It shows a severe lack of critical thinking if nothing else.