given the examples I laid out
how would it be misguided?
because I believe that in this context pacifism is flat out and across the board, immoral.
Last resort? No, that's not what pacifism is. It wouldn't be pacifism if war were the last resort, by definition.
In fact I agree war should be the last resort. Although that's an ideal that cannot be achieved in every circumstance and indeed in some circumstances it should never be the last resort. For instance in the case of a neighbor in imminent danger with our full and complete knowledge that he/she will suffer harm without our intervention. Then as you weigh the options you discover that it's a possibility that diplomacy may work. But military action will guarantee the saving of your neighbor with a far greater certainty. In such a circumstance war becomes the first option.
Playing with hypotheticals will make a case for the last resort over the first resort and vice versa and all kinds of in-betweens. But to say war should always be the last resort would be ignoring lethal realities that could lead you to an immoral decision, one that ends up with your neighbor's death. And of course it works in the other direction as well. It's not the extremes that are most important, but the gradations in between that have more potential for dilemma, as we see today.