Both you and your parent comment are incorrect. Self-defense vs first strike becomes a gradient very quickly. And the biggest issue is that the person interpreting what happened is usually the one that used the violence.

But back to the main point, there is a world of difference between "self-defense" and "violence used to prevent additional violence". Self-defense is immediate: someone is punching you, so you punch back. The other thing... it doesn't have to be. In my mind, self-defense is justified. But self-defense is defined as "have no other reasonable option", and thus is fairly narrow. If you can negotiate, if you can protect your interests by deterring the enemy, if you can eliminate the enemy without violence, by say sanctions, etc. then you have options and it's not self-defense. Also, self-defense is not the condition where violence is the best option. It's only self-defense when violence is the only option.

Perhaps violence is justified when it's not self-defense, but I don't think you can call any first-strike "self-defense" in order to gain the high moral ground.