Without going down the rabbit-hole of arguing about specific hypothetical situations ("What if the woman in the dark alley was your daughter? What if the guy was smaller than you and you think you could take him, but you don't know if he's armed? Isn't calling the police a degree of selflessness too, since the guy might get out on bail and then come after you?") I'll point out that there is a difference between saying "This is moral and therefore you should do it all the time" (which is unrealistic) and "This is moral and therefore it should be your goal" (which is not). So if I value selflessness over selfishness, that doesn't mean I think it's reasonable or realistic for anyone to be selfless all the time. Just like most of us value honesty over dishonesty, but hardly anyone expects everyone (or even themselves) to always be completely and utterly honest.

You admit yourself it's a matter of degree, but seem to think I am taking a binary approach.

Also, selflessness and empathy aren't just Judeo-Christian values. Pretty much every society has encouraged them, regardless of religion or lack thereof. Even Soviet Russia, Nazi Germany, and the Mongols and other notoriously warlike cultures espoused them, just carving out exceptions and rationalizations for why it didn't apply to "enemies" (and in practice creating societies where actually conforming to any kind of humane standard of behavior was a negative survival trait).