This is where pure philosophy and reality meets. There is no way for any human beings to be omniscient with perfect information. Therefore, we'd have to make a judgment using logic and deduction. Do you really think these guys were just having "harmless fun" or were they carrying malicious intent? My logic and deduction tells me they were probably malicious. There is a reason why emotional distress law suits are so hard to win; the exact reason you have stated: you can't really prove perspectives.