Dawkins was trying to use logic to analyze the probability of a god existing, using the creationists own arguments.
Actually Dawkins attempts to show "why there almost certainly is no God" (the title of chapter 4 of his book) using his own arguments. Examining again his logic:
1. Complex things are improbable as to coming about by chance: "The greater the statistical improbability, the less plausible is chance as a solution: that is what improbable means."
2. Life is very complex and therefore improbable by chance.
3. Any God capable of designing the universe [and complex life] would have to be more complex than his creation, and therefore more improbable. Any entity capable of intelligently designing something would have to be even more improbable than his design."a God capable of designing a universe, or anything else, would have to be complex and statistically improbable."
4. Therefore God (being very improbable) almost certainly does not exist.
Though creationists believe points 1. and 2., they are also believed by Dawkins as being true as well. Hense, they are just as much his "own arguments" as creationists "own arguments". Points 3. and 4. are Dawkins' arguments, not creationists, especially his equating improbability of any God coming about by chance with improbability of any Gods existence.