Many creationists try to make a big deal out of the link between evolution and atheism. Those who stand up for teaching evolution are often branded as atheists, including many devout theists. It seems there are two central claims behind such links. The first claim is that evolution is incompatible with a belief in God - that it either leaves God redundant or diminishes our species to a mere accident. The second claim is that evolution is being used to push God out of the picture - that it's a materialist ideology masquerading as science.
The first case is one best left to theologians, but the second case pertains to the validity of evolution as a science. The relevant question seem to be whether something held for ideological reasons can also be valid. Even if it were true that evolution was purely materialist ideology whose leading proponents sought to exclude God, would this invalidate evolution as a science?
To look at this question I'm going to invoke a historical parallel. Jesus is the central figure to Christianity, without a historical Jesus most forms of Christianity would be wrong. So does the historical case for Jesus need exclusion on the basis that Christianity needs a historical Jesus?
I'm fairly sure I know the answer to this. Of course not! The case for a historical Jesus should be decided by the historical evidence. Indeed, I've heard the argument that the historical Jesus is the main reason to be a Christian.
So when it comes to evolution, even if there's people with an ideological agenda, surely evolution's status as a science depends on whether or not the theory is able to fit with observation and evidence. It could be that evolution is good science and good reason to be a materialist.
Interestingly enough, when it comes to evolution there is no divide among experts down religious lines. And when experts do speak about evolution, they talk about the evidence for evolution. Meanwhile the link between evolution and atheism is highlighted by creationists, who don't talk about evidence at all. It may be that Francis Collins has been brainwashed by materialists, or that he's not a True Christian™ if he's so willing to speak in favour of evolution, but either way such a statement shows where the ideological hand in the evolution discussion really lies...