atheists have to believe in evolutionism to deny a God and Creator
Not really, pete. It depends a certain amount what you mean by 'evolutionism', but there were plenty of athiests before Darwin, and indeed plenty of atheists today whose knowledge of Darwin's original proposal and its developments is more than a little shaky. If you simply mean not believing in a creator god or gods they need some other mechanism for how we came to be, then yes, I'd agree. But it is probably not a good idea to lump every other possibility than creationism under a single heading. And there's no logical reason why a person might not deny creationism and deny Darwin's theory [mind you, they would be rather an odd sort!]

i am aware that some christians claim to believe genesis and darwinism but i leave that to them to reconcile
But you are willing to regard them as Christians? I think that was Don's point. If I understand your phrase correctly, you are willing to accept them, but don't want to put words in your mouth.