I've tried to explain this exact point to many people with limited success. Most people don't understand that morality is very fluid and depends on the situation, culture and context. The example I always used to use was of someone who is starving stealing bread to survive - in most cases people can accept that that is a case where it is not immoral to steal. The things is the exact point at which you draw the line varies from person to person. The ultimate rule I suppose is that survival trumps anything and can overrule most if not all moral codes.