If defensive, “reactionary” violence is morally equivalent to unprompted aggressive violence, then all “good people” are destined for extinction.

In addition, if this is true, then first-strike is equally as moral as defensive response, meaning that massacring anyone you don't like is never immoral since it's the same as hitting back. Defensive has to be "better" than offensive, or there's no reason to not be aggressive and jingoistic at all times. It would lead to quite a nightmare world.