Chance are good that the second owner didn't know the Superchargers are paired, and would impact the speed of charging. Since we don't know if the Supercharger was busy and either the first or second owner could move to an empty unpaired space, we can only guess. It could be that the second owner simply did not know that clicking the button would interrupt the charge of another car. Its worth our own peace of mind and not worthy of the stress on our selves, to think of this as anything more than an accident or ignorance vice maliciousness. There's little value in getting upset over something like this. As we all gain more experience, EV etiquette will improve.