Note that Quakers never rejected the possibility of being killed for their beliefs, just the choice of killing others for them. Pacifism does not equate to passivism, after all: it simply means that they reject the notion of visiting violence on others.

It's also important to note that pacifism has been a divisive issue for Quakers from very early times. The play 'Sword of Peace' that's performed throughout the year in Snow Camp, NC, is about Meetings in the US struggling with the question of pacifism vs. the desire to aid their nascent country during the American Revolution. It was a debate for Friends during the US Civil War, both World Wars, Korea, Vietnam, and onwards – one of the tenets of Quakerism is the need to wrestle with those issues by listening to the 'still small voice within' rather than blindly accepting the dictates of others. For many Friends, the threat posed by British colonial rule, the Confederacy, or Nazi Germany simply outweighed the demands of their conscience not to bear arms.

Friends often refer to the anecdote of William Penn asking George Fox (one of the founders of Quakerism) whether Penn should stop wearing his sword because he was now a Quaker. Fox told him, 'wear thy sword as long as thee is able' — meaning he should give it up because his conscience dictated it, not because he was a Quaker.

Thanks for the background! I am admittedly not very familiar with Quakers or their history. The clarification in the first part of your post helps with the context, I'll agree it's an entirely different story if it's a moral that is strived for but not strictly enforced (follow this or you're not one of us)