shomer negiah

Question

i was just wondering......lets say someone was getting a ride somewhere from a non-jew and he is a man. In the car he says " hi my name is this and sticks out his hand to shake yours. what r u supposed to do? do u shake his hand back? b/c if you dont, isnt it a chillel Hashem to make the non-jew feel stupid and uncomfortable? and wat r u supposed to say?"im jewish, i dont touch men"??? They wouldnt understand and would feel stupid and may look at us jews as if we were crazy and not polite.