Yeah, i've gotten used to these people in KoE. It's childish, but the best way to avoid losing Mirra is to just 'turn the other cheek' and get rekt one time, and then when you're in purgatory, you grab a drink, watch a video on youtube, and just wait out those 15 minutes. Usually, if it's just one PvP junkie passing through, and if you're not back within a minute or two they'll get bored waiting, and move on.
What you absolutely should not do, is pull out the victim card. That only attracts more unwanted attention.
Having said that, let's be honest about it, guys... You know you're doing something not quite right when Southpark spoofs your ass!
PvP junkies are a negative side-effect of the mmoRPG genre, not the defining characteristic.