And how do you know that they have a Tzelem Elokim? It’s not even a definite fact that every Yid has one. Yes, it’s true that they are Hashem’s Maase Yadayim, but don’t stretch it.
Why do you feel that you have to find an excuse to behave appropriately? What’s wrong with the simple requirement of any human being to act like one?! The same reason you expect any non Jewish person not to spit you in the face or to cover his mouth when he sneezes or even not to steal, is the reason why you behave accordingly. The reason I stop by a red light is the same reason the guy on the opposite side does, not because of Dina Demalchusa – which doesn’t really apply here anyhow. That is what Reb Shlomo Zalman and the Mirrer Rosh Yeshiva were saying.