To approach what, for the want of a better term, we call the mythic portions of the Nikayas with the attitude that such categories as “mythic symbol” and “literally true” are absolutely opposed is to adopt an attitude that is out of time and place. It seems to me that in some measure we must allow both a literal and a psychological interpretation. Both are there in the texts.
If you can intentionally kill out of compassion, then fine, go ahead. But are you sure? Are you sure that what you think are friendliness and compassion are really friendliness and compassion? Are you sure that some subtle aversion and delusion have not surfaced in the mind?