"One deeper assumption which I think all of us would agree about is that killing fellow human beings is a bad thing to do - and then we'd divide about what kind of circumstances might justify doing something like that; and also probably about what we mean by "human being"."

Very astute observation. And I think that one reason we have trouble discussing (and understanding each other) is that so many of the arguements that either side uses are either...

1. based on assumptions we make FOR the other side about what THEY must believe. I do think it is fair to point out inconsistencies -- but if you are going to do so, I think it is incumbent upon you to LISTEN to their response -- they may actually have an answer for what YOU think is an inconsistency.

2. the above but they have become unassailible cliches.

3. defenses for what we WANT to believe rather than reasons for why we believe what we believe.