Creationists do not debate that micro-evolution occurs. They debate over macro-evolution. There is tons of evidence of micro-evolution, but very little on macro-evolution.
Micro-evolution is science. It is something we have observed, we have tested, we have reproduced, we have predicted. If we change a creature's environment and then observe the changes over a period of time, it will adapt to its new environment. This is not contested. What is contested is that this is evolution and not devolution.
My wife and I have a gene pool that our children will pull from. When that child is born, it will lack genetic information that previously existed between my wife and I. The child will either get a dominate or a recessive gene from me, and one from my wife. It cannot get a dominate gene if my wife and I did not already have it. So if both my wife and I had a dominant gene and a recessive gene and the child only has recessive, then information has been lost in this localized environment. This may make the child better suited, and it may not. Survival of the fittest will come into play and weed out poor combinations.
Micro-evolution can occur to such a degree that a new species is created. Still, no new information has been introduced, but rather information has been lost. As a result, a creationist will accept that speciazation does occur and we see it happening today.
A creationist believes that it is extremely rare (if even possible) that new genetic information is introduced in the creation of an organism and that this genetic modification is actually beneficial to the organism.
Macro-evolution is far from being scientifically proven. There is science that leads us to believe it is possible, but it is not something we can reproduce, and the number of times it has been postulated to have been observed are extremely rare.
So on that note, both Creationism and evolution are both articles of faith.