one might say that this person didn't really mean it, they just acted automatically, on reflex
I would ask, does not questioning your own impulses absolve you of all moral culpability?
personally, I think not; we each have the responsibility to interrogate our automatic actions
admittedly, I do kill gnats, roaches sometimes, when within the confines of my home
and mosquitos, whatever they are, with extreme prejudice
but otherwise, I take care to not terminate life when it's avoidable
the ew factor aside, roaches are fascinatingly complex beings