You have to pin them on the knowledge argument.
Evolution is a way of understanding and describing change in the universe.
'goddidit' is not.
If at any time they are using god-talk, you should ask them to define what they mean. You have to put them up to scientific standards. If they don't do that then they are not interested in understanding reality.
More here:
http://www.youtube.com/view_play_lis...F546E2613114CB
(esp the first two)