One can be a believer and not deny evolution.
One who is an atheist or agnostic must by necessity believe in evolution. If intelligent design or some other matter suggesting God action is proved then ipso facto they are wrong.
A agree with Coulter what people miss in this discussion is not the religion of the intelligent design believers but the religion of the Darwinists. The reason even a tepid, incomplete discussion of intelligent design cannot occur in the public schools--is the Darwinist religion cannot permit what to them is a heresy. Claiming no faith in God does not make one more objective or "scientific." Such claims themselves are leaps to faith just like any ohter religion.
" One who is an atheist or agnostic must by necessity believe in evolution."
In the absence of an invisible man in the sky, the atheist falls back on observation and reason to try and untangle reality. If the theory of evolution fits the facts, it isn't surprising he will go with it, as opposed to 'believing' something in the absence of observation but rather swallowing whole the superstition of others.
Your subsuming reason under belief does you a disservice, but since people aren't reasoned into religious beliefs, it's a waste of time to trying reasoning them out of it.
"One who is an atheist or agnostic must by necessity believe in evolution."
You are incorrect. There are other possible world views that an atheist might adopt. For example, an atheist might be able to believe that the universe exists only in his own mind, and that it is generated as he lives. That sort of experiential world has been written about a number of times.
However, most atheists are people who generally accept the theory of evolution to be the mechanism of speciation. If physical evidence pointed in another direction, then they'd consider that, too.
The only explanation that atheists reject out of hand is the idea of a supernatural creator.
I don't know. I've read some agnostics who think Darwinism is bogus. They don't accept creation, or some form of intelligent design; they're just convinced that Darwinism isn't the correct explanation.