
You're admitting a lot more than that.  You are admitting that
your morals are situational.   You are admitting that the actions
of other people and the situation you are in help to determine
how you judge the moral significance of one of your own actions.

If you employ X degree of force, that's not moral, but if you employ
X degree of force, but previously someone else has employed Y degree
of force, and the situation is thus-and-so, that *is* moral.

This is quite different from saying "Employing force on other people
is immoral, period.   Unfortunately, from time to time we are obliged
to do this immoral thing for reasons of self-preservation, and so
we have to bear the moral consequences of that.

For what it's worth - and yes, I know you claim to be an agnostic -
it's this ability to re-label things from "immoral" to "moral" 
that I find one of the *least* attractive qualities of the religious
mind.