An argument that is instigated by someone who is typically passive could
come as a surprise today, Moonchild. This unexpected outburst could reveal
resentment that you had no idea existed. You could respond with stunned
silence, but later on, you would probably regret not saying anything to stand
up for yourself. Since this person rarely reveals deep feelings like this, you
don't want to discourage it, but you really should have a frank discussion.
Take some time to think and then schedule a pow-wow to clear the air.