South Korea was in a defensive war with North Korea.

In the same way the confederacy was in a defensive with the US, that is, sure, but in both cases the north was completely justified on liberatory grounds

You just tricked yourself. If they are in a defensive war like you said then there must also be an attacker. In all the cases you mentioned the faction attacking is armed with way more weapons being used for attack. This highlight exactly what i'm saying, which is that weapons are mostly made for attack not for defense.