Why do some Christians trust creationist opinions over scientific ideas that have been worked out by many scientists over many years? Presumably they are quite happy to take medicines that have also been developed by scientists over many years, without feeling the need to question its effectiveness.
I think the answer is that just as Galileo showed that the sun does not revolve round the earth, evolution challenges Christians to accept that they are not the centre of the universe. A rather humbling notion, especially for the self exalting kind of Christians who tend to be the ones who are very pro creationism.